Review the full syntax for SQL joins in MariaDB. This guide details the structure of table references, index hints, and various join types supported in SELECT, UPDATE, and DELETE statements.
MariaDB supports the following JOIN syntaxes for the table_references part of statements and multiple-table and statements:
A table reference is also known as a join expression.
Each table can also be specified as db_name.tabl_name. This allows to write queries which involve multiple databases. See for syntax details.
The syntax of table_factor is an extension to the SQL Standard. The latter accepts only table_reference, not a list of them inside a pair of parentheses.
This is a conservative extension if we consider each comma in a list of table_reference items as equivalent to an inner join. Consider this query:
It is equivalent to this query:
In general, parentheses can be ignored in join expressions containing only inner join operations. MariaDB also supports nested joins (see ).
A table subquery is specified as a parenthesized query and must contain a following derived table name (specified as alias in the above syntax specification).
You can optionally specify a list of column names in parenthesis.
Here, the table subquery for t1 will be materialized and named dt2, with column names ic1, ic2, ic3. These column names are used outside the subquery.
You cannot optionally specify a list of column names in parenthesis.
See also .
See for more information about the FOR SYSTEM_TIME syntax.
Index hints can be specified to affect how the MariaDB optimizer makes use of indexes. For more information, see .
When is active, the Oracle-style + syntax can be used. For example, the following two queries are identical:
and
Similarly, the following two queries are identical:
and
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table_references:
table_reference [, table_reference] ...
table_reference:
table_factor
| join_table
table_factor (<= MariaDB 11.6):
tbl_name [PARTITION (partition_list)]
[query_system_time_period_specification] [[AS] alias] [index_hint_list]
| table_subquery [query_system_time_period_specification] [AS] alias
| ( table_references )
| { ON table_reference LEFT OUTER JOIN table_reference
ON conditional_expr }
table_factor (>= MariaDB 11.7):
tbl_name [PARTITION (partition_list)]
[query_system_time_period_specification] [[AS] alias] [index_hint_list]
| table_subquery [query_system_time_period_specification] [AS] alias [(column_name_list)]
| ( table_references )
| { ON table_reference LEFT OUTER JOIN table_reference
ON conditional_expr }
join_table:
table_reference [INNER | CROSS] JOIN table_factor [join_condition]
| table_reference STRAIGHT_JOIN table_factor
| table_reference STRAIGHT_JOIN table_factor ON conditional_expr
| table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference join_condition
| table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN table_factor
join_condition:
ON conditional_expr
| USING (column_list)
query_system_time_period_specification:
FOR SYSTEM_TIME AS OF point_in_time
| FOR SYSTEM_TIME BETWEEN point_in_time AND point_in_time
| FOR SYSTEM_TIME FROM point_in_time TO point_in_time
| FOR SYSTEM_TIME ALL
point_in_time:
[TIMESTAMP] expression
| TRANSACTION expression
index_hint_list:
index_hint [, index_hint] ...
index_hint:
USE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])
| IGNORE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
| FORCE {INDEX|KEY}
[{FOR {JOIN|ORDER BY|GROUP BY}] (index_list)
index_list:
index_name [, index_name] ...SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)SELECT ic1, ic2, ic3 FROM
(
SELECT c1, c2, c3 FROM t1 GROUP BY c1
) dt2 (ic1, ic2, ic3)
JOIN t2 ON t2.c1 = dt2.ic1
WHERE c2 > 0
GROUP BY ic1SELECT * FROM t1 LEFT JOIN t2 ON t1.a = t2.b;SELECT * FROM t1, t2 WHERE t1.a = t2.b(+);SELECT * FROM t1 RIGHT JOIN t2 ON t1.a = t2.b;SELECT * FROM t1, t2 WHERE t1.a(+) = t2.b;SELECT left_tbl.*
FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id = right_tbl.id
WHERE right_tbl.id IS NULL;