次のようなSQLステートメントがあります。
SELECT colID
FROM tableName
WHERE ColDateStart <='$lowerDate'
AND ColDateStart>='$upperDate'
AND ColVcamID='$id1'
AND ColVlviID='$id2'
AND ColSomeID='$id3';
WHERE ステートメントのすべての列は、インデックス付きの列です。
これを実行すると、1 秒以上かかります。ただし、他の Id3 なしでこれを実行すると、パフォーマンスが大幅に向上します (0.03 秒)。
説明を実行すると、otherId3 で、otherId1 と otherId3 を使用したインデックス マージが使用されます。ただし、otherId3 を削除すると、otherId2 の単一のインデックスが使用されます。
otherId3 を追加するとパフォーマンスに影響するのはなぜですか?
テーブル構造:
+----------------------+-------------+------+-----+---------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------------+-------------+------+-----+---------------------+----------------+
| ColID | int(11) | NO | PRI | NULL | auto_increment |
| ColCustID | int(11) | NO | MUL | 0 | |
| ColCarrID | int(11) | NO | MUL | NULL | |
| ColTariID | int(11) | NO | MUL | 0 | |
| ColCarrierRef | varchar(30) | NO | MUL | | |
| ColNumbID | int(11) | NO | MUL | 0 | |
| ColVlviID | int(11) | NO | MUL | NULL | |
| ColVcamID | int(11) | NO | MUL | NULL | |
| ColSomeID | int(11) | NO | MUL | NULL | |
| ColVlnsID | int(11) | NO | MUL | NULL | |
| ColNGNumber | varchar(12) | NO | | | |
| ColOrigNumber | varchar(16) | NO | MUL | NULL | |
| ColCLIRestrictedFlag | int(2) | NO | | NULL | |
| ColOrigLocality | varchar(11) | NO | MUL | | |
| ColOrigAreaCode | varchar(11) | NO | MUL | | |
| ColTermNumber | varchar(16) | NO | MUL | NULL | |
| ColBatchNumber | varchar(10) | NO | | | |
| ColDateStart | date | NO | MUL | 0000-00-00 | |
| ColDateClear | date | NO | | 0000-00-00 | |
| ColTimeStart | time | NO | | 00:00:00 | |
| ColTimeClear | time | NO | | 00:00:00 | |
| ColCallLength | time | NO | | 00:00:00 | |
| ColRingLength | time | NO | | 00:00:00 | |
| ColEffectiveFlag | smallint(1) | NO | MUL | NULL | |
| ColUnansweredFlag | smallint(1) | NO | MUL | NULL | |
| ColEngagedFlag | smallint(1) | NO | | NULL | |
| ColRecID | int(11) | NO | MUL | NULL | |
| ColCreatedUserID | int(11) | NO | | 0 | |
| ColCreatedDatetime | datetime | NO | MUL | 0000-00-00 00:00:00 | |
| ColDirection | int(1) | NO | MUL | NULL | |
+----------------------+-------------+------+-----+---------------------+----------------+
インデックス
+-------+------------+-------------------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------+------------+-------------------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+
| tableName | 0 | PRIMARY | 1 | ColID | A | 18031283 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_ColCustID | 1 | ColCustID | A | 1339 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_ColNumbID | 1 | ColNumbID | A | 24366 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colOrigNumber | 1 | colOrigNumber | A | 4507820 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colOrigLocality | 1 | colOrigLocality | A | 36873 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colOrigAreaCode | 1 | colOrigAreaCode | A | 696 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colTermNumber | 1 | colTermNumber | A | 137643 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colDateStart | 1 | colDateStart | A | 3639 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colEffectiveFlag | 1 | colEffectiveFlag | A | 2 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colUnansweredFlag | 1 | colUnansweredFlag | A | 2 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colEngagedFlag | 1 | colUnansweredFlag | A | 2 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colTariID | 1 | colTariID | A | 91 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_CustID_DateStart | 1 | colCustID | A | 1339 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_CustID_DateStart | 2 | colDateStart | A | 693510 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_NumbID_DateStart | 1 | colNumbID | A | 24366 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_NumbID_DateStart | 2 | colDateStart | A | 4507820 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colRecID | 1 | colRecID | A | 214658 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colCarrierRef | 1 | colCarrierRef | A | 6010427 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colCustID_colTermNumber | 1 | colCustID | A | 1339 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colCustID_colTermNumber | 2 | colTermNumber | A | 143105 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colCreatedDatetime | 1 | colCreatedDatetime | A | 474507 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colDirection | 1 | colDirection | A | 2 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colVlviID | 1 | colVlviID | A | 4133 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colSomeID | 1 | colSomeID | A | 10 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colVcamID | 1 | colVcamID | A | 7 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colVlnsID | 1 | colVlnsID | A | 18 | NULL | NULL | | BTREE | |
| tableName | 1 | idx_colCarrID | 1 | colCarrID | A | 4 | NULL | NULL | | BTREE | |
+-------+------------+-------------------------------+--------------+---------------------+-----------+-------------+----------+--------+------+------------+---------+