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- SELECT
- t.TABLE_SCHEMA AS `db`, t.TABLE_NAME AS `table`, s.INDEX_NAME AS `index name`
- , s.COLUMN_NAME AS `field name`, s.SEQ_IN_INDEX `seq in index`, s2.max_columns AS`# cols`
- , s.CARDINALITY AS `card`, t.TABLE_ROWS AS `est rows`
- , ROUND(((s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) * 100), 2) AS `sel %`
- FROM INFORMATION_SCHEMA.STATISTICS s
- INNER JOIN INFORMATION_SCHEMA.TABLES t
- ON s.TABLE_SCHEMA = t.TABLE_SCHEMA AND s.TABLE_NAME = t.TABLE_NAME
- INNER JOIN (
- SELECT TABLE_SCHEMA, TABLE_NAME, INDEX_NAME, MAX(SEQ_IN_INDEX) AS max_columns
- FROM INFORMATION_SCHEMA.STATISTICS WHERE TABLE_SCHEMA != 'mysql'
- GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME
- ) AS s2
- ON s.TABLE_SCHEMA = s2.TABLE_SCHEMA AND
- s.TABLE_NAME = s2.TABLE_NAME AND
- s.INDEX_NAME = s2.INDEX_NAME
- WHERE t.TABLE_SCHEMA != 'mysql'/* Filter out the mysql system DB */
- AND t.TABLE_ROWS > 10 /* Only tables with some rows */
- AND s.CARDINALITY IS NOT NULL/* Need at least one non-NULL value in the field */
- AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00 /* unique indexes are perfect anyway */
- ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME /* DESC for best non-uniqueindexes */
- LIMIT 10;
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