This'll probably show my ignorance, but can someone explain why this
select uses index on ob_vl_parametry.info_cs when that column is not
used anywhere in the query?
mysql> EXPLAIN SELECT vp.id
-> FROM ob_vl_parametry_zbozi zp, ob_vl_parametry vp,
-> ob_vl_parametry_kategorie vpk
-> WHERE zp.id_zbozi IN (409)
-> AND vp.id = zp.id_par
-> AND vp.id = vpk.id_par
-> ORDER BY zp.poradi\G
*************************** 1. row ***************************
table: vp
type: index
possible_keys: PRIMARY
key: info_cs
key_len: 1
ref: NULL
rows: 59
Extra: Using index; Using temporary; Using filesort
*************************** 2. row ***************************
table: vpk
type: ref
possible_keys: PRIMARY
key: PRIMARY
key_len: 8
ref: vp.id
rows: 8
Extra: Using index
*************************** 3. row ***************************
table: zp
type: ref
possible_keys: id_par
key: id_par
key_len: 4
ref: vp.id
rows: 126
Extra: Using where; Using index
3 rows in set (0.00 sec)
mysql> show keys from ob_vl_parametry\G
*************************** 1. row ***************************
Table: ob_vl_parametry
Non_unique: 0
Key_name: PRIMARY
Seq_in_index: 1
Column_name: id
Collation: A
Cardinality: 59
Sub_part: NULL
Packed: NULL
Null:
Index_type: BTREE
Comment:
*************************** 2. row ***************************
Table: ob_vl_parametry
Non_unique: 1
Key_name: info_cs
Seq_in_index: 1
Column_name: info_cs
Collation: A
Cardinality: 29
Sub_part: 1
Packed: NULL
Null:
Index_type: BTREE
Comment:
*************************** 3. row ***************************
Table: ob_vl_parametry
Non_unique: 1
Key_name: nazev_cs
Seq_in_index: 1
Column_name: nazev_cs
Collation: A
Cardinality: 59
Sub_part: NULL
Packed: NULL
Null:
Index_type: BTREE
Comment:
3 rows in set (0.01 sec)
--
If you cc me or remove the list(s) completely I'll most likely ignore
your message. see http://www.eyrie.org./~eagle/faqs/questions.html
--
MySQL General Mailing List
For list archives: http://lists.mysql.com/mysql
To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
