mirror of
https://github.com/getml/sqlgen.git
synced 2026-01-02 07:30:17 -06:00
65 lines
1.8 KiB
Markdown
65 lines
1.8 KiB
Markdown
# String Operations
|
|
|
|
The `sqlgen` library provides a set of string functions for use in queries. These functions are type-safe and map to the appropriate SQL operations for the target database.
|
|
|
|
## Motivating Example
|
|
Suppose you want to create a report of people with their full names in uppercase, and also want to trim any whitespace from their last names:
|
|
|
|
```cpp
|
|
struct PersonReport {
|
|
std::string full_name;
|
|
std::string last_name_trimmed;
|
|
};
|
|
|
|
const auto get_reports =
|
|
select_from<Person>(
|
|
concat(upper("last_name"_c), ", ", "first_name"_c).as<"full_name">(),
|
|
trim("last_name"_c).as<"last_name_trimmed">()
|
|
)
|
|
| to<std::vector<PersonReport>>;
|
|
```
|
|
|
|
This query produces a list of people with their full names in the format "LASTNAME, Firstname" (with the last name in uppercase) and ensures the last name has no leading or trailing whitespace.
|
|
|
|
## String Functions
|
|
|
|
### `length`
|
|
Returns the length of a string.
|
|
|
|
```cpp
|
|
length(trim("first_name"_c)) | as<"length_first_name">
|
|
```
|
|
|
|
### `lower` / `upper`
|
|
Converts a string to lowercase or uppercase.
|
|
|
|
```cpp
|
|
lower("first_name"_c) | as<"first_name_lower">
|
|
upper("first_name"_c) | as<"first_name_upper">
|
|
```
|
|
|
|
### `ltrim`, `rtrim`, `trim`
|
|
Removes whitespace (or a specified character) from the left, right, or both sides of a string.
|
|
|
|
```cpp
|
|
ltrim("first_name"_c) | as<"ltrimmed_name">
|
|
rtrim("last_name"_c) | as<"rtrimmed_name">
|
|
trim("nickname"_c) | as<"trimmed_nickname">
|
|
// With custom characters:
|
|
ltrim("field"_c, "_ ") | as<"ltrimmed_field">
|
|
```
|
|
|
|
### `replace`
|
|
Replaces all occurrences of a substring with another substring.
|
|
|
|
```cpp
|
|
replace("first_name"_c, "Bart", "Hugo") | as<"first_name_replaced">
|
|
```
|
|
|
|
### `concat`
|
|
Concatenates multiple strings or expressions.
|
|
|
|
```cpp
|
|
concat("first_name"_c, " ", "last_name"_c) | as<"full_name">
|
|
concat(upper("last_name"_c), ", ", "first_name"_c) | as<"full_name">
|
|
``` |