This page describes the categorization scheme for the SQL statements and links to lists of the statements that fall into each category. It also describes notions, like the `WITH` clause, that need careful explanation and have applicability across two or more statement kinds.

{{< note title="Under construction." >}}

Future versions of the YSQL documentation will explain further such common notions.

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## Classification of SQL statements

### Data definition language (DDL)

**[DDL](./statements/#data-definition-language-ddl)** statements define the structures in a database, change their definitions, and remove them by using `CREATE`, `ALTER`, and `DROP` commands respectively.

### Data manipulation language (DML)

**[DML](./statements/#data-manipulation-language-dml)** statements query and modify the contents of a database.

### Data control language (DCL)

**[DCL](./statements/#data-control-language-dcl)** statements protect the definitions of database objects and the data the tables store using a regime of rules and privileges that control the scope and power of DDL and DML statements.

### Transaction control language (TCL)

**[TCL](./statements/#transaction-control-language-tcl)** statements manage transactions of operations on the database.

### Session and system control

**[Statements in this class](./statements/#session-and-system-control)** allow database parameters to be set at the session or the system level.

### Performance control

**[Statements in this class](./statements/#performance-control)** support the preparation of SQL statements, and their subsequent execution, to allow a more efficient execution by _binding_ actual arguments to placeholders in a SQL statement that is compiled just once, per session, rather than _every_ time actual arguments are presented. The canonical example of this feature is provided by the actual arguments that a `WHERE` clause restriction uses or the actual values than an `INSERT` statement will use.

In the performance control class, the [`EXPLAIN`](./statements/perf_explain/) statement shows what access methods a DML statement will use and (for statements with joins) the join order and method.

## The WITH clause

**[The `WITH` clause](./with-clause/)** (sometimes known as the _common table expression_) can be used as part of a `SELECT` statement, an `INSERT` statement, an `UPDATE` statement, or a `DELETE` statement. For this reason, the functionality is described in a dedicated section.