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---
sidebar_position: 1
sidebar_label: Query Builder
description: TinyORM's database query builder provides a convenient, fluent interface to creating and running database queries. It can be used to perform most database operations in your application. The query builder uses QSqlQuery parameter binding to protect your application against SQL injection attacks. There is no need to clean or sanitize strings passed to the query builder as query bindings.
keywords: [c++ orm, sql, c++ sql, c++ query builder, database, query builder, tinyorm]
---
import Link from '@docusaurus/Link'
# Database: Query Builder
- [Introduction](#introduction)
- [Running Database Queries](#running-database-queries)
- [Chunking Results](#chunking-results)
- [Aggregates](#aggregates)
- [Select Statements](#select-statements)
- [Raw Expressions](#raw-expressions)
- [Joins](#joins)
- [Basic Where Clauses](#basic-where-clauses)
- [Where Clauses](#where-clauses)
- [Or Where Clauses](#or-where-clauses)
- [Where Not Clauses](#where-not-clauses)
- [Additional Where Clauses](#additional-where-clauses)
- [Condition Operator Overriding](#condition-operator-overriding)
- [Logical Grouping](#logical-grouping)
- [Advanced Where Clauses](#advanced-where-clauses)
- [Where Exists Clauses](#where-exists-clauses)
- [Subquery Where Clauses](#subquery-where-clauses)
- [Ordering, Grouping, Limit & Offset](#ordering-grouping-limit-and-offset)
- [Ordering](#ordering)
- [Grouping](#grouping)
- [Limit & Offset](#limit-and-offset)
- [Insert Statements](#insert-statements)
- [Upserts](#upserts)
- [Update Statements](#update-statements)
- [Increment & Decrement](#increment-and-decrement)
- [Delete Statements](#delete-statements)
- [Truncate Statement](#truncate-statement)
- [Pessimistic Locking](#pessimistic-locking)
- [Debugging](#debugging)
## Introduction
<div className="api-stability alert alert--success">
<Link to='/stability#stability-indexes'>__Stability: 2__</Link> - Stable
</div>
TinyORM's database query builder provides a convenient, fluent interface to creating and running database queries. It can be used to perform most database operations in your application.
The TinyORM query builder uses `QSqlQuery` parameter binding to protect your application against SQL injection attacks. There is no need to clean or sanitize strings passed to the query builder as query bindings.
:::danger
`QSqlQuery` does not support binding column names. Therefore, you should never allow user input to dictate the column names referenced by your queries, including "order by" columns.
:::
:::danger
The `QMYSQL` Qt driver contains a bug, if your table contains a `json` column type, then you must explicitly name columns other than `json` columns instead of the `*` shorthand, otherwise, you will get an empty result, or all column values will be invalid QVariant-s, or it may even return half of the columns. The `QPSQL` driver returns correct results and doesn't have problem with `json` columns. It was fixed in the Qt ~5.15.12~, 6.2.7, 6.5.0 [QTBUG-101680](https://bugreports.qt.io/browse/QTBUG-101680).
:::
## Running Database Queries
#### Retrieving All Rows From A Table
You may use the `table` method provided by the `DB` facade to begin a query. The `table` method returns a fluent query builder instance for the given table, allowing you to chain more constraints onto the query and then finally retrieve the results of the query using the `get` method:
```cpp
#include <orm/db.hpp>
// Log a list of all of the application's users
auto query = DB::table("users")->get();
while (query.next())
qDebug() << "id :" << query.value("id").toULongLong() << ";"
<< "name :" << query.value("name").toString();
```
The `get` method returns a `QSqlQuery` containing the results of the query where each result can be accessed by `QSqlQuery::next` method, look into the `QSqlQuery` documentation how to obtain results from the "query". You may access each column's value by `QSqlQuery::value` method. The first `bool` return value is the value returned from `QSqlQuery::exec` method:
```cpp
#include <QDebug>
#include <orm/db.hpp>
auto users = DB::table("users")->get();
while(users.next())
qDebug() << users.value("name").toString();
```
#### Retrieving A Single Row / Column From A Table
If you just need to retrieve a single row from a database table, you may use the `QueryBuilder::first` method. This method will return a `QSqlQuery` object, on which was internally called `QSqlQuery::first` method. This method retrieves the first record in the result, if available, and positions the query on the retrieved record:
```cpp
auto user = DB::table("users")->whereEq("name", "John").first();
user.value("email").toString();
```
If you don't need an entire row, you may extract a single value from a record using the `value` method. This method will return the value of the column directly as `QVariant`:
```cpp
auto email = DB::table("users")->whereEq("name", "John").value("email").toString();
```
To retrieve a single row by its `id` column value, use the `find` method. This method retrieves the first record in the result, if available, and positions the query on the retrieved record:
```cpp
auto user = DB::table("users")->find(3);
user.value("email").toString();
```
#### Retrieving A List Of Column Values
If you would like to retrieve the `QList<QVariant>` instance containing the values of a single column, you may use the `pluck` method. In this example, we'll retrieve a collection of user titles:
```cpp
#include <QDebug>
#include <orm/db.hpp>
const auto titles = DB::table("users")->pluck("title");
for (const auto &title : titles)
qDebug() << title.value<QString>();
```
You may specify the column that the resulting collection should use as its keys by providing a second argument to the `pluck` method, following example returns the `std::map<QString, QVariant>` of "titles" keyed by "names":
```cpp
#include <orm/db.hpp>
auto titles = DB::table("users")->pluck<QString>("title", "name");
for (auto &&[name, title] : titles)
qDebug() << name << ":" << title.value<QString>();
```
You may also use `pluck<quint64>("name", "id")`, it returns the `std::map<quint64, QVariant>` of "names" keyed by its "ids".
:::note
This second `pluck` overload returns `std::map<T, QVariant>` so you have to provide a template argument for the key type.
:::
#### Concatenate column values
The `implode` method can be used to join column values. For example, you may use this method to concatenate prices with the `, ` character as the glue:
```cpp
DB::table("orders")->where("price", ">", 100).implode("price", ", ");
```
### Chunking Results
If you need to work with thousands of database records, consider using the `chunk` method provided by the `DB` facade. This method retrieves a small chunk of results at a time and feeds each chunk into a lambda expression for processing. For example, let's retrieve the entire `users` table in chunks of 100 records at a time:
```cpp
DB::table("users")->orderBy("id").chunk(100, [](QSqlQuery &users, const int page)
{
while (users.next()) {
//
}
return true;
});
```
You may stop further chunks from being processed by returning `false` from the closure:
```cpp
DB::table("users")->orderBy("id").chunk(100, [](QSqlQuery &users, const int page)
{
// Process the records...
return false;
});
```
If you are updating database records while chunking results, your chunk results could change in unexpected ways. If you plan to update the retrieved records while chunking, it is always best to use the `chunkById` method instead. This method will automatically paginate the results based on the record's primary key:
```cpp
DB::table("users")
->whereEq("active", false)
.orderBy("id")
.chunkById(100, [](QSqlQuery &users, const int /*unused*/)
{
while (users.next())
DB::table("users")
->whereEq("id", users.value("id"))
.update({{"active", true}});
return true;
});
```
:::caution
When updating or deleting records inside the chunk lambda expression, any changes to the primary key or foreign keys could affect the chunk query. This could potentially result in records not being included in the chunked results, it can be avoided using the `chunkById` method.
:::
### Aggregates
The query builder also provides a variety of methods for retrieving aggregate values like `count`, `max`, `min`, `avg`, and `sum`. You may call any of these methods after constructing your query:
```cpp
#include <orm/db.hpp>
auto users = DB::table("users")->count();
auto price = DB::table("orders")->max("price");
```
Of course, you may combine these methods with other clauses to fine-tune how your aggregate value is calculated:
```cpp
auto price = DB::table("orders")
->whereEq("finalized", 1)
.avg("price");
```
#### Determining If Records Exist
Instead of using the `count` method to determine if any records exist that match your query's constraints, you may use the `exists` and `doesntExist` methods:
```cpp
if (DB::table("orders")->whereEq("finalized", 1).exists()) {
// ...
}
if (DB::table("orders")->whereEq("finalized", 1).doesntExist()) {
// ...
}
```
## Select Statements
#### Specifying A Select Clause
You may not always want to select all columns from a database table. Using the `select` method, you can specify a custom "select" clause for the query:
```cpp
#include <orm/db.hpp>
auto users = DB::table("users")
->select({"name", "email as user_email"})
.get();
```
The `distinct` method allows you to force the query to return distinct results:
```cpp
auto users = DB::table("users")->distinct().get();
```
If you already have a query builder instance and you wish to add a column to its existing select clause, you may use the `addSelect` method:
```cpp
auto query = DB::table("users")->select("name");
auto users = query.addSelect("age").get();
```
:::note
You can also pass subqueries to the `select` and `addSelect` methods. A subquery can be a lambda expression, raw string, or the `QueryBuilder` instance.
:::
## Raw Expressions
Sometimes you may need to insert an arbitrary string into a query. To create a raw string expression, you may use the `raw` method provided by the `DB` facade:
```cpp
auto users = DB::table("users")
->select(DB::raw("count(*) as user_count, status"))
.where("status", "<>", 1)
.groupBy("status")
.get();
```
:::danger
Raw statements will be injected into the query as strings, so you should be extremely careful to avoid creating SQL injection vulnerabilities.
:::
### Raw Methods
Instead of using the `DB::raw` method, you may also use the following methods to insert a raw expression into various parts of your query. **Remember, TinyORM can not guarantee that any query using raw expressions is protected against SQL injection vulnerabilities.**
#### `selectRaw`
The `selectRaw` method can be used in place of `addSelect(DB::raw(...))`. This method accepts an optional vector of bindings as its second argument:
```cpp
auto orders = DB::table("orders")
->selectRaw("price * ? as price_with_tax", {1.0825})
.get();
```
#### `fromRaw`
The `fromRaw` method may be used to provide a raw string as the value of the "from" clause:
```cpp
auto users = DB::connection("postgres").query()
->fromRaw("(select id, name from users where id < ?) as u", {5})
.where("id", "<", 3)
.get();
```
#### `whereRaw / orWhereRaw`
The `whereRaw` and `orWhereRaw` methods can be used to inject a raw "where" clause into your query. These methods accept an optional vector of bindings as their second argument:
```cpp
auto orders = DB::table("orders")
->whereRaw("price > IF(state = \"TX\", ?, 100)", {200})
.get();
```
### `groupByRaw`
The `groupByRaw` method may be used to provide a raw string as the value of the `group by` clause:
```cpp
auto orders = DB::table("orders")
->select({"city", "state"})
.groupByRaw("city, state")
.get();
```
#### `havingRaw / orHavingRaw`
The `havingRaw` and `orHavingRaw` methods may be used to provide a raw string as the value of the "having" clause. These methods accept an optional vector of bindings as their second argument:
```cpp
auto orders = DB::table("orders")
->select({"department", DB::raw("SUM(price) as total_sales")})
.groupBy("department")
.havingRaw("SUM(price) > ?", {2500})
.get();
```
#### `orderByRaw`
The `orderByRaw` method may be used to provide a raw string as the value of the "order by" clause:
```cpp
auto orders = DB::table("orders")
->orderByRaw("updated_at - created_at DESC")
.get();
```
## Joins
#### Inner Join Clause
The query builder may also be used to add join clauses to your queries. To perform a basic "inner join", you may use the `join` method on a query builder instance. The first argument passed to the `join` method is the name of the table you need to join to, while the remaining arguments specify the column constraints for the join. You may even join multiple tables in a single query:
```cpp
#include <orm/db.hpp>
auto users = DB::table("users")
->join("contacts", "users.id", "=", "contacts.user_id")
.join("orders", "users.id", "=", "orders.user_id")
.select({"users.*", "contacts.phone", "orders.price"})
.get();
```
#### Left Join / Right Join Clause
If you would like to perform a "left join" or "right join" instead of an "inner join", use the `leftJoin` or `rightJoin` methods. These methods have the same signature as the `join` method:
```cpp
auto users = DB::table("users")
->leftJoin("posts", "users.id", "=", "posts.user_id")
.get();
auto users = DB::table("users")
->rightJoin("posts", "users.id", "=", "posts.user_id")
.get();
```
#### Cross Join Clause
You may use the `crossJoin` method to perform a "cross join". Cross joins generate a cartesian product between the first table and the joined table:
```cpp
auto sizes = DB::table("sizes")
->crossJoin("colors")
.get();
```
#### Advanced Join Clauses
You may also specify more advanced join clauses. To get started, pass a lambda expression as the second argument to the `join` method. The lambda expression will receive a `Orm::Query::JoinClause` instance which allows you to specify constraints on the "join" clause:
```cpp
#include <orm/db.hpp>
#include <orm/query/joinclause.hpp>
DB::table("users")
->join("contacts", [](auto &join)
{
join.on("users.id", "=", "contacts.user_id")
.orOn(...);
})
.get();
```
If you would like to use a "where" clause on your joins, you may use the `where` and `orWhere` methods provided by the `Orm::Query::JoinClause` instance. Instead of comparing two columns, these methods will compare the column against a value:
```cpp
DB::table("users")
->join("contacts", [](auto &join)
{
join.on("users.id", "=", "contacts.user_id")
.where("contacts.user_id", ">", 5);
})
.get();
```
#### Subquery Joins
You may use the `joinSub`, `leftJoinSub`, and `rightJoinSub` methods to join a query to a subquery. Each of these methods receives three arguments: the subquery, its table alias, and a lambda expression that defines the related columns. In this example, we will retrieve a collection of users where each user record also contains the `created_at` timestamp of the user's most recently published blog post:
```cpp
auto latestPosts = DB::table("posts")
->select({"user_id", DB::raw("MAX(created_at) as last_post_created_at")})
.whereEq("is_published", true)
.groupBy("user_id");
auto users = DB::table("users")
->joinSub(latestPosts, "latest_posts", [](auto &join)
{
join.on("users.id", "=", "latest_posts.user_id");
}).get();
```
## Basic Where Clauses
### Where Clauses
You may use the query builder's `where` method to add "where" clauses to the query. The most basic call to the `where` method requires three arguments. The first argument is the name of the column. The second argument is an operator, which can be any of the database's supported operators. The third argument is the value to compare against the column's value.
For example, the following query retrieves users where the value of the `votes` column is equal to `100` and the value of the `age` column is greater than `35`:
```cpp
auto users = DB::table("users")
->where("votes", "=", 100)
.where("age", ">", 35)
.get();
```
For convenience, if you want to verify that a column is `=` to a given value, you may call `whereEq` method. Similar `XxxEq` methods are also defined for other commands:
```cpp
auto users = DB::table("users")->whereEq("votes", 100).get();
```
As previously mentioned, you may use any operator that is supported by your database system:
```cpp
auto users = DB::table("users")
->where("votes", ">=", 100)
.get();
auto users = DB::table("users")
->where("votes", "<>", 100)
.get();
auto users = DB::table("users")
->where("name", "like", "T%")
.get();
```
You may also pass a `QList<Orm::WhereItem>` of conditions to the `where` function. Each `Orm::WhereItem` structure should contain the four arguments typically passed to the `where` method:
```cpp
auto users = DB::table("users")
->where({
{"status", 1}, // "=" by default
{"subscribed", 1, "<>"},
}).get();
```
### Or Where Clauses
When chaining together calls to the query builder's `where` method, the "where" clauses will be joined together using the `and` operator. However, you may use the `orWhere` or `orWhereEq` method to join a clause to the query using the `or` operator. The `orWhere` method accepts the same arguments as the `where` method:
```cpp
auto users = DB::table("users")
->where("votes", ">", 100)
.orWhere("name", "=", "John")
.orWhereEq("name", "Jack")
.get();
```
If you need to group an "or" condition within parentheses, you may pass a lambda expression as the first argument to the `orWhere` method:
```cpp
auto users = DB::table("users")
->where("votes", ">", 100)
.orWhere([](auto &query)
{
query.whereEq("name", "Abigail")
.where("votes", ">", 50);
})
.get();
```
The example above will produce the following SQL:
```sql
select * from users where votes > 100 or (name = "Abigail" and votes > 50)
```
### Condition Operator Overriding
The `where` method overload with a `QList<Orm::WhereItem>` as the first argument joins conditions using the `and` operator by default:
```cpp
auto users = DB::table("users")
->where({
{"first_name", "John"},
{"votes", 50, ">"},
}).get();
```
Conditions operator can be overridden by the fourth argument in the `Orm::WhereItem` structure:
```cpp
auto users = DB::table("users")
->where({
{"first_name", "John"},
{"votes", 50, ">", "or"},
}).get();
```
Or by the second `where` argument, in this case all conditions will be joined by this condition, but it is still possible to override them by the fourth argument in the `Orm::WhereItem` structure:
```cpp
auto users = DB::table("users")
->where({
{"first_name", "John"},
{"last_name", "Smith"},
{"votes", 50, ">", "and"},
}, "or")
.get();
```
The example above will produce the following SQL:
```sql
select * from users where (first_name = "John" or last_name = "Smith" and votes > 50)
```
:::tip
Still, it is a better idea to use [Logical Grouping](#logical-grouping) described few lines below, which allows better control of the parentheses.
:::
### Where Not Clauses
The `whereNot` and `orWhereNot` methods may be used to negate a given group of query constraints. For example, the following query excludes products that are on clearance or which have a price that is less than ten:
```cpp
auto products = DB::table("products")
->whereNot([](auto &query) {
query.whereEq("clearance", true)
.orWhere("price", "<", 10);
})
.get();
```
### Additional Where Clauses
**whereBetween / orWhereBetween**
The `whereBetween` method verifies that a column's value is between two values:
```cpp
auto users = DB::table("users")
->whereBetween("votes", {1, 100})
.get();
```
**whereNotBetween / orWhereNotBetween**
The `whereNotBetween` method verifies that a column's value lies outside of two values:
```cpp
auto users = DB::table("users")
->whereNotBetween("votes", {1, 100})
.get();
```
**whereBetweenColumns / orWhereBetweenColumns**
The `whereBetweenColumns` method verifies that a column's value is between two values in given columns:
```cpp
auto files = DB::table("files")
->whereBetweenColumns("quota", {"min_allowed_quota", "max_allowed_quota"})
.get();
```
**whereNotBetweenColumns / orWhereNotBetweenColumns**
The `whereNotBetweenColumns` method verifies that a column's value lies outside of two values in given columns:
```cpp
auto files = DB::table("files")
->whereNotBetweenColumns("quota", {"min_allowed_quota", "max_allowed_quota"})
.get();
```
**whereIn / whereNotIn / orWhereIn / orWhereNotIn**
The `whereIn` method verifies that a given column's value is contained within the given `QList<QVariant>`:
```cpp
auto users = DB::table("users")
->whereIn("id", {1, 2, 3})
.get();
```
The `whereNotIn` method verifies that the given column's value is not contained in the given `QList<QVariant>`:
```cpp
auto users = DB::table("users")
->whereNotIn("id", {1, 2, 3})
.get();
```
**whereNull / whereNotNull / orWhereNull / orWhereNotNull**
The `whereNull` method verifies that the value of the given column is `NULL`:
```cpp
auto users = DB::table("users")
->whereNull("updated_at")
.get();
```
The `whereNotNull` method verifies that the column's value is not `NULL`:
```cpp
auto users = DB::table("users")
->whereNotNull("updated_at")
.get();
```
**whereDate / whereTime / whereDay / whereMonth / whereYear**
The `whereDate` method may be used to compare a column's value against a date:
```cpp
auto users = DB::table("users")
->whereDate("created_at", EQ, QDate(2022, 11, 18))
.get();
```
The `whereTime` method may be used to compare a column's value against a specific time:
```cpp
auto users = DB::table("users")
->whereTime("created_at", "=", QTime(11, 14, 23))
.get();
```
The `whereDay` method may be used to compare a column's value against a specific day of the month:
```cpp
auto users = DB::table("users")
->whereDay("created_at", "<=", 15)
.get();
```
The `whereMonth` method may be used to compare a column's value against a specific month:
```cpp
auto users = DB::table("users")
->whereEqMonth("created_at", 12)
.get();
```
The `whereYear` method may be used to compare a column's value against a specific year:
```cpp
auto users = DB::table("users")
->whereEqYear("created_at", 2016)
.get();
```
The `whereDate` and `whereTime` methods also accept a `QDateTime` instance or you can pass values as a `QString` in `2022-12-31` or `09:15:11` formats.
The `whereDay`, `whereMoth`, and `whereYear` accept `QDate` or `QDateTime` instances, an integral number or a `QString` that contains an integral number.
:::info
All the above methods offer `whereEqXyz` and `orWhereXyz` shortcut methods.
:::
**whereColumn / orWhereColumn**
The `whereColumnEq` method may be used to verify that two columns are equal:
```cpp
auto users = DB::table("users")
->whereColumnEq("first_name", "last_name")
.get();
```
You may also pass a comparison operator to the `whereColumn` method:
```cpp
auto users = DB::table("users")
->whereColumn("updated_at", ">", "created_at")
.get();
```
You may also pass a `QList<Orm::WhereColumnItem>` of column comparisons to the `whereColumn` method. These conditions will be joined using the `and` operator:
```cpp
auto users = DB::table("users")
->whereColumn({
{"first_name", "last_name"},
{"updated_at", "created_at", ">"},
}).get();
```
Conditions operator can also be overridden by the fourth argument in the `Orm::WhereColumnItem` structure:
```cpp
auto users = DB::table("users")
->whereColumn({
{"first_name", "last_name"},
{"updated_at", "created_at", ">", "or"},
}).get();
```
Or by the second `whereColumn` argument:
```cpp
auto users = DB::table("users")
->whereColumn({
{"first_name", "last_name"},
{"updated_at", "created_at", ">"},
}, "or")
.get();
```
### Logical Grouping
Sometimes you may need to group several "where" clauses within parentheses in order to achieve your query's desired logical grouping. In fact, you should generally always group calls to the `orWhere` method in parentheses in order to avoid unexpected query behavior. To accomplish this, you may pass a lambda expression to the `where` method:
```cpp
auto users = DB::table("users")
->where("name", "=", "John")
.where([](auto &query)
{
query.where("votes", ">", 100)
.orWhere("title", "=", "Admin");
})
.get();
```
As you can see, passing a lambda expression into the `where` method instructs the query builder to begin a constraint group. The lambda expression will receive a query builder instance which you can use to set the constraints that should be contained within the parenthesis group. The example above will produce the following SQL:
```sql
select * from users where name = "John" and (votes > 100 or title = "Admin")
```
## Advanced Where Clauses
### Where Exists Clauses
The `whereExists` method allows you to write "where exists" SQL clauses. The `whereExists` method accepts a lambda expression which will receive a query builder instance, allowing you to define the query that should be placed inside of the "exists" clause:
```cpp
auto users = DB::table("users")
->whereExists([](auto &query)
{
query.select(DB::raw(1))
.from("orders")
.whereColumnEq("orders.user_id", "users.id");
})
.get();
```
Alternatively, you may provide a query object to the `whereExists` method instead of a lambda expression:
```cpp
// Ownership of the std::shared_ptr<QueryBuilder>
auto builder = DB::table("orders");
auto orders = builder->select(DB::raw(1))
.whereColumnEq("orders.user_id", "users.id");
auto users = DB::table("users")
->whereExists(orders)
.get();
```
Or directly:
```cpp
auto users = DB::table("users")
->whereExists(DB::table("orders")
->select(DB::raw(1))
.whereColumnEq("orders.user_id", "users.id"))
.get();
```
All of the examples above will produce the following SQL:
```sql
select * from users
where exists (
select 1
from orders
where orders.user_id = users.id
)
```
### Subquery Where Clauses
Sometimes you may need to construct a "where" clause that compares the results of a subquery to a given value. You may accomplish this by passing a lambda expression and a value to the `where` method. For example, the following query will retrieve all users who have a recent "membership" of a given type:
```cpp
#include "models/user.hpp"
auto users = User::whereEq([](auto &query)
{
query.select("type")
.from("membership")
.whereColumnEq("membership.user_id", "users.id")
.orderByDesc("membership.start_date")
.limit(1);
}, "Pro")->get();
```
Or, you may need to construct a "where" clause that compares a column to the results of a subquery. You may accomplish this by passing a column, operator, and lambda expression to the `where` method. For example, the following query will retrieve all income records where the amount is less than average;
```cpp
#include "models/income.hpp"
auto incomes = Income::where("amount", "<", [](auto &query)
{
query.selectRaw("avg(i.amount)").from("incomes as i");
})->get();
```
## Ordering, Grouping, Limit & Offset {#ordering-grouping-limit-and-offset}
### Ordering
#### The `orderBy` Method
The `orderBy` method allows you to sort the results of the query by a given column. The first argument accepted by the `orderBy` method should be the column you wish to sort by, while the second argument determines the direction of the sort and may be either `asc` or `desc`:
```cpp
auto users = DB::table("users")
->orderBy("name", "desc")
.get();
```
To sort by multiple columns, you may simply invoke `orderBy` as many times as necessary:
```cpp
auto users = DB::table("users")
->orderBy("name", "desc")
.orderBy("email", "asc")
.get();
```
#### The `latest` & `oldest` Methods
The `latest` and `oldest` methods allow you to easily order results by date. By default, the result will be ordered by the table's `created_at` column. Or, you may pass the column name that you wish to sort by:
```cpp
auto user = DB::table("users")
->latest()
.first();
```
#### Random Ordering
The `inRandomOrder` method may be used to sort the query results randomly. For example, you may use this method to fetch a random user:
```cpp
auto randomUser = DB::table("users")
->inRandomOrder()
.first();
```
#### Removing Existing Orderings
The `reorder` method removes all of the "order by" clauses that have previously been applied to the query:
```cpp
auto &query = DB::table("users")->orderBy("name");
auto unorderedUsers = query.reorder().get();
```
You may pass a column and direction when calling the `reorder` method in order to remove all existing "order by" clauses and apply an entirely new order to the query:
```cpp
auto &query = DB::table("users")->orderBy("name");
auto usersOrderedByEmail = query.reorder("email", "desc").get();
```
### Grouping
#### The `groupBy` & `having` Methods
As you might expect, the `groupBy` and `having` methods may be used to group the query results. The `having` method's signature is similar to that of the `where` method:
```cpp
auto users = DB::table("users")
->groupBy("account_id")
.having("account_id", ">", 100)
.get();
```
You may pass multiple items to the `groupBy` method to group by multiple columns:
```cpp
auto users = DB::table("users")
->groupBy({"first_name", "status"})
.having("account_id", ">", 100)
.get();
```
### Limit & Offset {#limit-and-offset}
#### The `skip` & `take` Methods
You may use the `skip` and `take` methods to limit the number of results returned from the query or to skip a given number of results in the query:
```cpp
auto users = DB::table("users")->skip(10).take(5).get();
```
Alternatively, you may use the `limit` and `offset` methods. These methods are functionally equivalent to the `take` and `skip` methods, respectively:
```cpp
auto users = DB::table("users")
->offset(10)
.limit(5)
.get();
```
## Insert Statements
The query builder also provides an `insert` method that may be used to insert records into the database table. The `insert` method accepts the `QVariantMap` of column names and values:
```cpp
DB::table("users")->insert({
{"email", "kayla@example.com"},
{"votes", 0},
});
```
<Link id='multi-insert-overload' />
You may insert several records at once by passing a `QList<QString>` for column names as the first argument and `QList<QList<QVariant>>` for values as the second argument. Each `QList<QVariant>` represents a record that should be inserted into the table. This overload is useful for multi-insert and allows to specify column names only once:
```cpp
DB::table("users")->insert({"email", "votes"},
{
{"picard@example.com", 0},
{"janeway@example.com", 0},
});
```
You may also insert several records at once by passing a `QList<QVariantMap>`. Each `QVariantMap` represents a record that should be inserted into the table:
```cpp
DB::table("users")->insert({
{{"email", "picard@example.com"}, {"votes", 0}},
{{"email", "janeway@example.com"}, {"votes", 0}},
});
```
The `insertOrIgnore` method will ignore duplicate record errors while inserting records into the database and also provides the same overloads like the `insert` method. When using this method, you should be aware that duplicate record errors will be ignored and other types of errors may also be ignored depending on the database engine. For example, `insertOrIgnore` will [bypass MySQL's strict mode](https://dev.mysql.com/doc/refman/en/sql-mode.html#ignore-effect-on-execution):
```cpp
DB::table("users")->insertOrIgnore({"id", "email"},
{
{1, "sisko@example.com"},
{2, "archer@example.com"},
});
DB::table("users")->insertOrIgnore({
{{"id", 1}, {"email", "sisko@example.com"}},
{{"id", 2}, {"email", "archer@example.com"}},
});
```
#### Auto-Incrementing IDs
If the table has an auto-incrementing id, use the `insertGetId` method to insert a record and then retrieve the ID:
```cpp
auto id = DB::table("users")->insertGetId({
{"email", "john@example.com"},
{"votes", 0},
});
```
### Upserts
The `upsert` method will insert records that do not exist and update the records that already exist with new values that you may specify. The method's first argument consists of the values to insert or update, while the second argument lists the column(s) that uniquely identify records within the associated table. The method's third and final argument is a vector of columns that should be updated if a matching record already exists in the database:
```cpp
DB::table("flights")->upsert(
{{{"departure", "Oakland"}, {"destination", "San Diego"}, {"price", 99}},
{{"departure", "Chicago"}, {"destination", "New York"}, {"price", 150}}},
{"departure", "destination"},
{"price"}
);
```
In the example above, TinyORM will attempt to insert two records. If a record already exists with the same `departure` and `destination` column values, TinyORM will update that record's `price` column.
:::caution
All databases except SQL Server require the columns in the second argument of the `upsert` method to have a "primary" or "unique" index. In addition, the MySQL database driver ignores the second argument of the `upsert` method and always uses the "primary" and "unique" indexes of the table to detect existing records.
:::
:::info
Row and column aliases will be used with the MySQL server >=8.0.19 instead of the VALUES() function as is described in the MySQL [documentation](https://dev.mysql.com/doc/refman/9.0/en/insert-on-duplicate.html). The MySQL server version is auto-detected and can be overridden in the [configuration](/database/getting-started.mdx#configuration).
:::
## Update Statements
In addition to inserting records into the database, the query builder can also update existing records using the `update` method. The `update` method, accepts a `QList<Orm::UpdateItem>` of column and value pairs, indicating the columns to be updated and returns a `std::tuple<int, QSqlQuery>` . You may constrain the `update` query using `where` clauses:
```cpp
auto [affected, query] = DB::table("users")
->whereEq("id", 1)
.update({{"votes", 1}});
```
:::note
An `update` and `delete` are affecting statements, so they return `std::tuple<int, QSqlQuery>`.
:::
#### Update Or Insert
Sometimes you may want to update an existing record in the database or create it if no matching record exists. In this scenario, the `updateOrInsert` method may be used. The `updateOrInsert` method accepts two arguments: a vector of conditions by which to find the record, and a vector of column and value pairs indicating the columns to be updated.
The `updateOrInsert` method will attempt to locate a matching database record using the first argument's column and value pairs. If the record exists, it will be updated with the values in the second argument. If the record can not be found, a new record will be inserted with the merged attributes of both arguments:
```cpp
DB::table("users")
->updateOrInsert(
{{"email", "john@example.com"}, {"name", "John"}},
{{"votes", 2}}
);
```
### Increment & Decrement {#increment-and-decrement}
The query builder also provides convenient methods for incrementing or decrementing the value of a given column. Both of these methods accept at least one argument: the column to modify. A second argument may be provided to specify the amount by which the column should be incremented or decremented:
```cpp
DB::table("users")->increment<int>("votes");
DB::table("users")->increment("votes", 5);
DB::table("users")->decrement<int>("votes");
DB::table("users")->decrement("votes", 5.2); // float or double type
```
You may also specify additional columns to update during the operation as a `QList<Orm::UpdateItem>`:
```cpp
DB::table("users")->increment("votes", 1, {{"name", "John"}});
```
You should constrain `increment`, `decrement` by `where` to update only specific record in the database, otherwise a column in all records will be modified.
```cpp
DB::table("users")->whereEq("id", 1).increment("votes", 5);
```
## Delete Statements
The query builder's `remove`, or an alias `deleteRow` method may be used to delete records from the table. You may constrain `delete` statements by adding "where" clauses before calling the `delete` method:
```cpp
DB::table("users")->remove();
DB::table("users")->where("votes", ">", 100).remove();
```
:::note
`delete` can not be used as the method name because it is the reserved word.
:::
You may also pass record `id` to the `remove` method as the first argument, it is the shortcut method, which internally calls `where`:
```cpp
DB::table("users")->remove(2);
```
### Truncate Statement
If you wish to truncate an entire table, which will remove all records from the table and reset the auto-incrementing ID to zero, you may use the `truncate` method:
```cpp
DB::table("users")->truncate();
```
#### Table Truncation & PostgreSQL
When truncating a PostgreSQL database, the `CASCADE` behavior will be applied. This means that all foreign key related records in other tables will be deleted as well.
## Pessimistic Locking
The query builder also includes a few functions to help you achieve "pessimistic locking" when executing your `select` statements. To execute a statement with a "shared lock", you may call the `sharedLock` method. A shared lock prevents the selected rows from being modified until your transaction is committed:
```cpp
DB::table("users")
->where("votes", ">", 100)
.sharedLock()
.get();
```
Alternatively, you may use the `lockForUpdate` method. A "for update" lock prevents the selected records from being modified or from being selected with another shared lock:
```cpp
DB::table("users")
->where("votes", ">", 100)
.lockForUpdate()
.get();
```
## Debugging
You may use the `dd` and `dump` methods while building a query to dump the current query bindings and SQL. The `dd` method will display the debug information and then stop executing using the `exit(1)`. The `dump` method will display the debug information and continue executing:
```cpp
DB::table("users")->where("votes", ">", 100).dd();
DB::table("users")->where("votes", ">", 100).dump();
```
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