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在说明系统数据库之前，先来看下MySQL在数据字典方面的演变历史：mysql> SELECT IF(COUNT(*) = 0,‘Not exists!‘,‘Exists!‘) AS ‘result‘ FROM information_schema.tables WHERE table_schema = ‘new_feature‘ AND table_name = ‘t1‘; +-------------+ | result | +-------------+ | Not exists! | +-------------+ 1 row in set (0.00 sec)
DELIMITER $$
USE `new_feature`$$
DROP PROCEDURE IF EXISTS `sp_table_exists`$$
CREATE DEFINER=`root`@`localhost` PROCEDURE `sp_table_exists`(
IN db_name VARCHAR(64),
IN tb_name VARCHAR(64),
OUT is_exists VARCHAR(60)
)
BEGIN
DECLARE no_such_table CONDITION FOR 1146;
DECLARE EXIT HANDLER FOR no_such_table
BEGIN
SET is_exists = ‘Not exists!‘;
END;
SET @stmt = CONCAT(‘select 1 from ‘,db_name,‘.‘,tb_name);
PREPARE s1 FROM @stmt;
EXECUTE s1;
DEALLOCATE PREPARE s1;
SET is_exists = ‘Exists!‘;
END$$
DELIMITER ;mysql> call sp_table_exists(‘new_feature‘,‘t1‘,@result); Query OK, 0 rows affected (0.00 sec) mysql> select @result; +-------------+ | @result | +-------------+ | Not exists! | +-------------+ 1 row in set (0.00 sec)
mysql> CALL table_exists(‘new_feature‘,‘t1‘,@v_is_exists); Query OK, 0 rows affected (0.00 sec) mysql> SELECT IF(@v_is_exists = ‘‘,‘Not exists!‘,@v_is_exists) AS ‘result‘; +-------------+ | result | +-------------+ | Not exists! | +-------------+ 1 row in set (0.00 sec)
mysql> SELECT * FROM schema_unused_indexes; +---------------+-------------+--------------+ | object_schema | object_name | index_name | +---------------+-------------+--------------+ | new_feature | t1 | idx_log_time | | new_feature | t1 | idx_rank2 | +---------------+-------------+--------------+ 2 rows in set (0.00 sec)
mysql> SELECT * FROM statement_analysis WHERE db=‘new_feature‘ AND full_scan = ‘*‘ AND exec_count > 10\G
*************************** 1. row ***************************
query: SHOW STATUS
db: new_feature
full_scan: *
exec_count: 26
err_count: 0
warn_count: 0
total_latency: 74.68 ms
max_latency: 3.86 ms
avg_latency: 2.87 ms
lock_latency: 4.50 ms
rows_sent: 9594
rows_sent_avg: 369
rows_examined: 9594
rows_examined_avg: 369
rows_affected: 0
rows_affected_avg: 0
tmp_tables: 0
tmp_disk_tables: 0
rows_sorted: 0
sort_merge_passes: 0
digest: 475fa3ad9d4a846cfa96441050fc9787
first_seen: 2015-11-16 10:51:17
last_seen: 2015-11-16 11:28:13
*************************** 2. row ***************************
query: SELECT `state` , `round` ( SUM ... uration (summed) in sec` DESC
db: new_feature
full_scan: *
exec_count: 12
err_count: 0
warn_count: 12
total_latency: 16.43 ms
max_latency: 2.39 ms
avg_latency: 1.37 ms
lock_latency: 3.54 ms
rows_sent: 140
rows_sent_avg: 12
rows_examined: 852
rows_examined_avg: 71
rows_affected: 0
rows_affected_avg: 0
tmp_tables: 24
tmp_disk_tables: 0
rows_sorted: 140
sort_merge_passes: 0
digest: 538e506ee0075e040b076f810ccb5f5c
first_seen: 2015-11-16 10:51:17
last_seen: 2015-11-16 11:28:13
2 rows in set (0.01 sec)mysql> SELECT * FROM statement_analysis WHERE db=‘new_feature‘ AND tmp_tables > 0 ORDER BY tmp_tables DESC LIMIT 1\G
*************************** 1. row ***************************
query: SELECT `performance_schema` . ... name` . `SUM_TIMER_WAIT` DESC
db: new_feature
full_scan: *
exec_count: 2
err_count: 0
warn_count: 0
total_latency: 87.96 ms
max_latency: 59.50 ms
avg_latency: 43.98 ms
lock_latency: 548.00 us
rows_sent: 101
rows_sent_avg: 51
rows_examined: 201
rows_examined_avg: 101
rows_affected: 0
rows_affected_avg: 0
tmp_tables: 332
tmp_disk_tables: 15
rows_sorted: 0
sort_merge_passes: 0
digest: ff9bdfb7cf3f44b2da4c52dcde7a7352
first_seen: 2015-11-16 10:24:42
last_seen: 2015-11-16 10:24:42
1 row in set (0.01 sec)mysql> SELECT statement,total FROM user_summary_by_statement_type WHERE `user`=‘root‘ ORDER BY total DESC LIMIT 5; +-------------------+-------+ | statement | total | +-------------------+-------+ | jump_if_not | 17635 | | freturn | 3120 | | show_create_table | 289 | | Field List | 202 | | set_option | 190 | +-------------------+-------+ 5 rows in set (0.01 sec)
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原文地址：http://blog.csdn.net/yueliangdao0608/article/details/50032851
