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77 lines
2.4 KiB
Markdown
77 lines
2.4 KiB
Markdown
# `sqlgen::exec`
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The `sqlgen::exec` interface provides a way to execute raw SQL statements on a database connection. It's useful when you need to perform database operations that aren't covered by the type-safe interfaces, such as setting database-specific parameters or executing custom SQL statements.
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## Usage
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### Basic Execution
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Execute a raw SQL statement:
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```cpp
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const auto conn = sqlgen::postgres::connect(credentials);
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sqlgen::exec(conn, "SET TIME ZONE 'UTC';").value();
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```
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### Curried Execution
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You can also use a curried version of `exec` that takes the SQL statement first and returns a function that accepts the connection. This is useful for chaining operations:
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```cpp
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using namespace sqlgen;
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const auto query = exec("SET TIME ZONE 'UTC';");
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// Using with a connection reference
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const auto conn = postgres::connect(credentials);
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query(conn).value();
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// Or in a chain with other operations
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postgres::connect(credentials)
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.and_then(exec("SET TIME ZONE 'UTC';"))
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.value();
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```
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## Example: Full Query Composition
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Here's a complete example showing how to use `exec` within a chain of operations:
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```cpp
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using namespace sqlgen;
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const auto result = postgres::connect(credentials)
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.and_then(exec("SET TIME ZONE 'UTC';"))
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.and_then(drop<Person> | if_exists)
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.and_then(write(people))
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.and_then(read<std::vector<Person>>)
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.value();
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```
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This executes the following SQL statements in sequence:
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```sql
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SET TIME ZONE 'UTC';
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DROP TABLE IF EXISTS "Person";
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-- Table creation and data insertion via write
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-- Data retrieval via read
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```
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## Notes
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- The `Result<Ref<Connection>>` type provides error handling; use `.value()` to extract the result (will throw an exception if there's an error) or handle errors as needed
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- The function has two overloads:
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1. Takes a connection reference and SQL string
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2. Takes a `Result<Ref<Connection>>` and SQL string
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- The curried version is particularly useful when you want to:
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- Chain multiple database operations together
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- Pass the execution operation as a function to other operations
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- Use `exec` when you need to:
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- Execute database-specific commands
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- Set database parameters
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- Run custom SQL statements not covered by type-safe interfaces
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- Perform administrative tasks
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- Exercise caution when using `exec` with user-provided input to prevent SQL injection attacks
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- The SQL statement is executed as-is, so ensure it's compatible with your database dialect
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