MySQL supports the following JOIN syntax for the table_references part\nof SELECT statements and multiple-table DELETE and UPDATE statements:\n\ntable_references:\n    escaped_table_reference [, escaped_table_reference] ...\n\nescaped_table_reference:\n    table_reference\n  | { OJ table_reference }\n\ntable_reference:\n    table_factor\n  | join_table\n\ntable_factor:\n    tbl_name [PARTITION (partition_names)]\n        [[AS] alias] [index_hint_list]\n  | table_subquery [AS] alias\n  | ( table_references )\n\njoin_table:\n    table_reference [INNER | CROSS] JOIN table_factor [join_condition]\n  | table_reference STRAIGHT_JOIN table_factor\n  | table_reference STRAIGHT_JOIN table_factor ON conditional_expr\n  | table_reference {LEFT|RIGHT} [OUTER] JOIN table_reference join_condition\n  | table_reference NATURAL [{LEFT|RIGHT} [OUTER]] JOIN table_factor\n\njoin_condition:\n    ON conditional_expr\n  | USING (column_list)\n\nindex_hint_list:\n    index_hint [, index_hint] ...\n\nindex_hint:\n    USE {INDEX|KEY}\n      [FOR {JOIN|ORDER BY|GROUP BY}] ([index_list])\n  | IGNORE {INDEX|KEY}\n      [FOR {JOIN|ORDER BY|GROUP BY}] (index_list)\n  | FORCE {INDEX|KEY}\n      [FOR {JOIN|ORDER BY|GROUP BY}] (index_list)\n\nindex_list:\n    index_name [, index_name] ...\n\nA table reference is also known as a join expression.\n\nA table reference (when it refers to a partitioned table) may contain a\nPARTITION option, including a list of comma-separated partitions,\nsubpartitions, or both. This option follows the name of the table and\nprecedes any alias declaration. The effect of this option is that rows\nare selected only from the listed partitions or subpartitions. Any\npartitions or subpartitions not named in the list are ignored. For more\ninformation and examples, see\nhttp://dev.mysql.com/doc/refman/5.7/en/partitioning-selection.html.\n\nThe syntax of table_factor is extended in MySQL in comparison with\nstandard SQL. The standard accepts only table_reference, not a list of\nthem inside a pair of parentheses.\n\nThis is a conservative extension if each comma in a list of\ntable_reference items is considered as equivalent to an inner join. For\nexample:\n\nSELECT * FROM t1 LEFT JOIN (t2, t3, t4)\n                 ON (t2.a = t1.a AND t3.b = t1.b AND t4.c = t1.c)\n\nis equivalent to:\n\nSELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)\n                 ON (t2.a = t1.a AND t3.b = t1.b AND t4.c = t1.c)\n\nIn MySQL, JOIN, CROSS JOIN, and INNER JOIN are syntactic equivalents\n(they can replace each other). In standard SQL, they are not\nequivalent. INNER JOIN is used with an ON clause, CROSS JOIN is used\notherwise.\n\nIn general, parentheses can be ignored in join expressions containing\nonly inner join operations. MySQL also supports nested joins. See\nhttp://dev.mysql.com/doc/refman/5.7/en/nested-join-optimization.html.\n\nIndex hints can be specified to affect how the MySQL optimizer makes\nuse of indexes. For more information, see\nhttp://dev.mysql.com/doc/refman/5.7/en/index-hints.html. Optimizer\nhints and the optimizer_switch system variable are other ways to\ninfluence optimizer use of indexes. See\nhttp://dev.mysql.com/doc/refman/5.7/en/optimizer-hints.html, and\nhttp://dev.mysql.com/doc/refman/5.7/en/switchable-optimizations.html.\n\nURL: http://dev.mysql.com/doc/refman/5.7/en/join.html\n\n