Spec-Zone .ru
спецификации, руководства, описания, API
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Spec-Zone .ru
спецификации, руководства, описания, API
|
SHOW {INDEX | INDEXES | KEYS} {FROM | IN} tbl_name [{FROM | IN} db_name] [WHERE expr]
SHOW
INDEX returns table index information. The format resembles that of the SQLStatistics
call in ODBC. This statement requires some privilege for any column in the table.
SHOW
INDEX returns the following fields:
Table
The name of the table.
Non_unique
0 if the index cannot contain duplicates, 1 if it can.
Key_name
The name of the index. If the index is the primary key, the name is always PRIMARY.
Seq_in_index
The column sequence number in the index, starting with 1.
Column_name
The column name.
How the column is sorted in the index. In MySQL, this can have values "A" (Ascending) or NULL (Not sorted).
An estimate of the number of unique values in the index. This is updated by running ANALYZE TABLE or myisamchk -a. Cardinality is counted based on statistics stored as integers, so the
value is not necessarily exact even for small tables. The higher the cardinality, the greater the
chance that MySQL uses the index when doing joins.
Sub_part
The number of indexed characters if the column is only partly indexed, NULL if the entire column is indexed.
Packed
Indicates how the key is packed. NULL if it is not.
Null
Contains YES if the column may contain NULL values and '' if not.
Index_type
The index method used (BTREE, FULLTEXT,
HASH, RTREE).
Comment
Information about the index not described in its own column, such as disabled if the index is disabled.
Index_comment
Any comment provided for the index with a COMMENT attribute when the
index was created.
You can use db_name.tbl_name
as an alternative to the tbl_name FROM db_name
SHOW INDEX FROM mytable FROM mydb;SHOW INDEX FROM mydb.mytable;
The WHERE clause can be given to select rows using more general conditions, as
discussed in Section 20.32, "Extensions to SHOW Statements".
You can also list a table's indexes with the mysqlshow -k db_name tbl_name command.