Defining tables

sqlgen provides a type-safe way to define database tables using C++ structs. It automatically handles table creation, schema management, and nullability through C++ types.

Usage

Basic Table Definition

Define a table using a simple C++ struct:

struct People {
    std::string first_name;
    std::string last_name;
    uint age;
};

When you write data to this table, it will be automatically created if it doesn't exist:

const auto people = std::vector<People>(...);
const auto result = sqlgen::write(conn, people);

This generates SQL similar to:

CREATE TABLE IF NOT EXISTS "People"(
    "first_name" TEXT NOT NULL,
    "last_name" TEXT NOT NULL,
    "age" INTEGER NOT NULL
);

Custom Table Names

Override the default table name using a static member:

struct People {
    constexpr static const char* tablename = "PEOPLE";
    
    std::string first_name;
    std::string last_name;
    uint age;
};

This generates SQL with the custom table name:

CREATE TABLE IF NOT EXISTS "PEOPLE"(
    "first_name" TEXT NOT NULL,
    "last_name" TEXT NOT NULL,
    "age" INTEGER NOT NULL
);

Custom Schemas

Define a table within a specific schema:

struct People {
    constexpr static const char* schema = "my_schema";
    
    std::string first_name;
    std::string last_name;
    uint age;
};

This generates SQL with the schema specification:

CREATE TABLE IF NOT EXISTS "my_schema"."People"(
    "first_name" TEXT NOT NULL,
    "last_name" TEXT NOT NULL,
    "age" INTEGER NOT NULL
);

Nullable Fields

As we have seen, all columns are non-nullable by default. But what if we do want nullability?

As with reflect-cpp, std::optional, std::shared_ptr and std::unique_ptr are interpreted as nullable types. So you can create nullable fields as follows:

struct People {
    rfl::PrimaryKey<std::string> first_name;
    std::string last_name;
    std::optional<uint> age;
};

Notes

All fields are non-nullable by default
Nullable fields can be defined using:
- std::optional<T>
- std::shared_ptr<T>
- std::unique_ptr<T>
Use std::nullopt or nullptr to represent NULL values
The exact SQL generated may vary between database dialects
Table names are inferred from struct names by default
Custom table names and schemas can be specified using static members

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