1. Overview

select-stmt: hide

The SELECT statement is used to query the database. The result of a SELECT is zero or more rows of data where each row has a fixed number of columns. A SELECT statement does not make any changes to the database.

The "select-stmt" syntax diagram above attempts to show as much of the SELECT statement syntax as possible in a single diagram, because some readers find that helpful. The following "factored-select-stmt" is an alternative syntax diagrams that expresses the same syntax but tries to break the syntax down into smaller chunks.

factored-select-stmt: show

Note that there are paths through the syntax diagrams that are not allowed in practice. Some examples:

• A VALUES clause can be the first element in a compound SELECT that uses a WITH clause, but a simple SELECT that consists of just a VALUES clause cannot be preceded by a WITH clause.
• The WITH clause must occur on the first SELECT of a compound SELECT. It cannot follow a compound-operator.

These and other similar syntax restrictions are described in the text.

The SELECT statement is the most complicated command in the SQL language. To make the description easier to follow, some of the passages below describe the way the data returned by a SELECT statement is determined as a series of steps. It is important to keep in mind that this is purely illustrative - in practice neither SQLite nor any other SQL engine is required to follow this or any other specific process.

2. Simple Select Processing

The core of a SELECT statement is a "simple SELECT" shown by the select-core and simple-select-stmt syntax diagrams below. In practice, most SELECT statements are simple SELECT statements.

simple-select-stmt: hide