# 查询当前运行的SQL ,获取当前性能较弱的SQL
SHOW FULL PROCESSLIST;
SELECT * FROM `information_schema`.processlist WHERE Command ='Query' ;
# 查看表索引
SHOW INDEX FROM qp_ttx_callback_record ;
;
#查看表列
SHOW COLUMNS FROM qp_ttx_callback_record ;
#查看Char列最长的字符
SELECT max(length(collectionNo)) , AVG(length(collectionNo)) FROM pt_package_collection ;
#查找当前列的区分度,趋向1则分布越均匀, 通常CHAR类型的列通过截断来实现索引性能提升。建议区分度在0.8或以上
SELECT count(DISTINCT ColumnName)/count(*) FROM Tabel_name ;
#增加索引
ALTER TABLE qpu_org /* DROP INDEX idx_parentId_orgType_status ; */ADD INDEX idx_parentId_orgType_status(parentId,orgType,STATUS)