The SELECT
statement retrieves rows from the database.
Examples
Select all columns from the table tbl
:
SELECT * FROM tbl;
Select the rows from tbl
:
SELECT j FROM tbl WHERE i = 3;
Perform an aggregate grouped by the column i
:
SELECT i, sum(j) FROM tbl GROUP BY i;
Select only the top 3 rows from the tbl
:
SELECT * FROM tbl ORDER BY i DESC LIMIT 3;
Join two tables together using the USING
clause:
SELECT * FROM t1 JOIN t2 USING (a, b);
Use column indexes to select the first and third column from the table tbl
:
SELECT #1, #3 FROM tbl;
Select all unique cities from the addresses table:
SELECT DISTINCT city FROM addresses;
Return a STRUCT
by using a row variable:
SELECT d
FROM (SELECT 1 AS a, 2 AS b) d;
Syntax
The SELECT
statement retrieves rows from the database. The canonical order of a SELECT
statement is as follows, with less common clauses being indented:
SELECT ⟨select_list⟩
FROM ⟨tables⟩
USING SAMPLE ⟨sample_expression⟩
WHERE ⟨condition⟩
GROUP BY ⟨groups⟩
HAVING ⟨group_filter⟩
WINDOW ⟨window_expression⟩
QUALIFY ⟨qualify_filter⟩
ORDER BY ⟨order_expression⟩
LIMIT ⟨n⟩;
Optionally, the SELECT
statement can be prefixed with a WITH
clause.
As the SELECT
statement is so complex, we have split up the syntax diagrams into several parts. The full syntax diagram can be found at the bottom of the page.
SELECT
Clause
The SELECT
clause specifies the list of columns that will be returned by the query. While it appears first in the clause, logically the expressions here are executed only at the end. The SELECT
clause can contain arbitrary expressions that transform the output, as well as aggregates and window functions. The DISTINCT
keyword ensures that only unique tuples are returned.
Column names are case-insensitive. See the Rules for Case Sensitivity for more details.
FROM
Clause
The FROM
clause specifies the source of the data on which the remainder of the query should operate. Logically, the FROM
clause is where the query starts execution. The FROM
clause can contain a single table, a combination of multiple tables that are joined together, or another SELECT
query inside a subquery node.
SAMPLE
Clause
The SAMPLE
clause allows you to run the query on a sample from the base table. This can significantly speed up processing of queries, at the expense of accuracy in the result. Samples can also be used to quickly see a snapshot of the data when exploring a data set. The SAMPLE
clause is applied right after anything in the FROM
clause (i.e., after any joins, but before the where clause or any aggregates). See the Samples page for more information.
WHERE
Clause
The WHERE
clause specifies any filters to apply to the data. This allows you to select only a subset of the data in which you are interested. Logically the WHERE
clause is applied immediately after the FROM
clause.
GROUP BY
and HAVING
Clauses
The GROUP BY
clause specifies which grouping columns should be used to perform any aggregations in the SELECT
clause. If the GROUP BY
clause is specified, the query is always an aggregate query, even if no aggregations are present in the SELECT
clause.
WINDOW
Clause
The WINDOW
clause allows you to specify named windows that can be used within window functions. These are useful when you have multiple window functions, as they allow you to avoid repeating the same window clause.
QUALIFY
Clause
The QUALIFY
clause is used to filter the result of WINDOW
functions.
ORDER BY
, LIMIT
and OFFSET
Clauses
ORDER BY
, LIMIT
and OFFSET
are output modifiers.
Logically they are applied at the very end of the query.
The ORDER BY
clause sorts the rows on the sorting criteria in either ascending or descending order.
The LIMIT
clause restricts the amount of rows fetched, while the OFFSET
clause indicates at which position to start reading the values.
VALUES
List
A VALUES
list is a set of values that is supplied instead of a SELECT
statement.
Row IDs
For each table, the rowid
pseudocolumn returns the row identifiers based on the physical storage.
CREATE TABLE t (id INTEGER, content VARCHAR);
INSERT INTO t VALUES (42, 'hello'), (43, 'world');
SELECT rowid, id, content FROM t;
rowid | id | content |
---|---|---|
0 | 42 | hello |
1 | 43 | world |
In the current storage, these identifiers are contiguous unsigned integers (0, 1, …) if no rows were deleted. Deletions introduce gaps in the rowids which may be reclaimed later. Therefore, it is strongly recommended not to use rowids as identifiers.
Tip The
rowid
values are stable within a transaction.
If there is a user-defined column named
rowid
, it shadows therowid
pseudocolumn.
Common Table Expressions
Full Syntax Diagram
Below is the full syntax diagram of the SELECT
statement: