SHOW {INDEX | INDEXES | KEYS} {FROM | IN}tbl_name
[{FROM | IN}db_name
]
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.
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
. If not, the column contains
NO
.
Contains YES
if the column may contain
NULL
values and ''
if
not.
Index_type
The index method used (BTREE
,
FULLTEXT
, HASH
,
RTREE
).
Comment
Various remarks.
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
syntax. These two
statements are equivalent:
tbl_name
FROM
db_name
SHOW INDEX FROM mytable FROM mydb; SHOW INDEX FROM mydb.mytable;
You can also list a table's indexes with the mysqlshow
-k db_name
tbl_name
command.
User Comments
This comment applies to http://dev.mysql.com/doc/refman/5.0/en/show-index.html
The mention of the LIKE keyword has been removed from http://dev.mysql.com/doc/refman/5.1/en/show-index.html. It is probably not a valid keyword for SHOW INDEXES.
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