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| -rw-r--r-- | Docs/manual.texi | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Docs/manual.texi b/Docs/manual.texi index 2e78af44557..1aed3ac6868 100644 --- a/Docs/manual.texi +++ b/Docs/manual.texi @@ -24779,6 +24779,8 @@ and check the query with @code{EXPLAIN} again. @xref{ALTER TABLE}. To see what indexes a table has, use @code{SHOW INDEX FROM tbl_name}. @item key +@findex USE INDEX +@findex IGNORE INDEX The @code{key} column indicates the key that MySQL actually decided to use. The key is @code{NULL} if no index was chosen. If MySQL chooses the wrong index, you can probably force @@ -32810,6 +32812,13 @@ because the column value may not yet be determined when the The @code{FROM table_references} clause indicates the tables from which to retrieve rows. If you name more than one table, you are performing a join. For information on join syntax, see @ref{JOIN, , @code{JOIN}}. +For each table specified, you may optionally specify an alias, as well as +make a suggestion to the optimiser what index to use or ignore. +@findex USE INDEX +@findex IGNORE INDEX +@example +table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)] +@end example @item You can refer to a column as @code{col_name}, @code{tbl_name.col_name}, or @@ -33099,6 +33108,8 @@ table_reference NATURAL [RIGHT [OUTER]] JOIN table_reference @end example Where @code{table_reference} is defined as: +@findex USE INDEX +@findex IGNORE INDEX @example table_name [[AS] alias] [USE INDEX (key_list)] [IGNORE INDEX (key_list)] @end example @@ -33194,6 +33205,8 @@ cases where the join optimiser puts the tables in the wrong order. @item @cindex hints +@findex USE INDEX +@findex IGNORE INDEX As of MySQL Version 3.23.12, you can give hints about which index MySQL should use when retrieving information from a table. This is useful if @code{EXPLAIN} shows that MySQL is |