Syntax

SELECT
    [ALL | DISTINCT | DISTINCTROW]
    [HIGH_PRIORITY]
    [STRAIGHT_JOIN]
    [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
    [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
    select_expr [, select_expr ...]
    [ FROM table_references [PARTITION (partition_list)]
      [{USE|FORCE|IGNORE} INDEX [FOR {JOIN|ORDER BY|GROUP BY}] ([index_list]) ]
      [WHERE where_condition]
      [GROUP BY {col_name | expr | position} [ASC | DESC], ... [WITH ROLLUP]]
      [HAVING where_condition]
      [ORDER BY {col_name | expr | position} [ASC | DESC], ...]
      [LIMIT {[offset,] row_count | row_count OFFSET offset}]
      [PROCEDURE procedure_name(argument_list)]
      [INTO OUTFILE 'file_name' [CHARACTER SET charset_name] [export_options]
         | INTO DUMPFILE 'file_name' | INTO var_name [, var_name] ]
      [[FOR UPDATE | LOCK IN SHARE MODE] [WAIT n | NOWAIT] ] ]

export_options:
    [{FIELDS | COLUMNS}
        [TERMINATED BY 'string']
        [[OPTIONALLY] ENCLOSED BY 'char']
        [ESCAPED BY 'char']
    ]
    [LINES
        [STARTING BY 'string']
        [TERMINATED BY 'string']
    ]

Description

SELECT is used to retrieve rows selected from one or more tables, and can include UNION statements and subqueries.

  • Each select_expr expression indicates a column or data that you want to retrieve. You must have at least one select expression. See Select Expressions below.
  • The FROM clause indicates the table or tables from which to retrieve rows. Use either a single table name or a JOIN expression. See JOIN for details. If no table is involved, FROM DUAL can be specified.
MariaDB starting with 10.0

The PARTITION clause was introduced in MariaDB 10.0. See Partition Pruning and Selection for details.

  • Each table can also be specified as db_name.tabl_name. Each column can also be specified as tbl_name.col_name or even db_name.tbl_name.col_name. This allows to write queries which involve multiple databases. See Identifier Qualifiers for syntax details.
  • The WHERE clause, if given, indicates the condition or conditions that rows must satisfy to be selected. where_condition is an expression that evaluates to true for each row to be selected. The statement selects all rows if there is no WHERE clause.
  • Use the ORDER BY clause to order the results.
  • Use the LIMIT clause allows you to restrict the results to only a certain number of rows, optionally with an offset.
  • Use the GROUP BY and HAVING clauses to group rows together when they have columns or computed values in common.

SELECT can also be used to retrieve rows computed without reference to any table.

Select Expressions

A SELECT statement must contain one or more select expressions, separated by commas. Each select expression can be one of the following:

  • The name of a column.
  • Any expression using functions and operators.
  • * to select all columns from all tables in the FROM clause.
  • tbl_name.* to select all columns from just the table tbl_name.

When specifying a column, you can either use just the column name or qualify the column name with the name of the table using tbl_name.col_name. The qualified form is useful if you are joining multiple tables in the FROM clause. If you do not qualify the column names when selecting from multiple tables, MariaDB will try to find the column in each table. It is an error if that column name exists in multiple tables.

You can quote column names using backticks. If you are qualifying column names with table names, quote each part separately as `tbl_name`.`col_name`.

If you use any grouping functions in any of the select expressions, all rows in your results will be implicitly grouped, as if you had used GROUP BY NULL.

DISTINCT

A query may produce some identical rows. By default, all rows are retrieved, even when their values are the same. To explicitly specify that you want to retrieve identical rows, use the ALL option. If you want duplicates to be removed from the resultset, use the DISTINCT option. DISTINCTROW is a synonym for DISTINCT. See also COUNT DISTINCT.

INTO

The INTO clause is used to specify that the query results should be written to a file or variable.

The reverse of SELECT INTO OUTFILE is LOAD DATA.

WAIT/NOWAIT

Set the lock wait timeout. See WAIT and NOWAIT.


MariaDB starting with 10.1.2

max_statement_time clause

By using max_statement_time in conjunction with SET STATEMENT, it is possible to limit the execution time of individual queries. For example:

SET STATEMENT max_statement_time=100 FOR 
  SELECT field1 FROM table_name ORDER BY field1;

See Also

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