SELECT id FROM tbl GROUP BY id HAVING COUNT(*) = N;
4. 計算兩個日子間的工作日 所謂工作日就是除出周六周日和節假日。
復制代碼 代碼如下:
SELECT COUNT(*) FROM calendar WHERE d BETWEEN Start AND Stop AND DAYOFWEEK(d) NOT IN(1,7) AND holiday=0;
5. 查找表中的主鍵
復制代碼 代碼如下:
SELECT k.column_name FROM information_schema.table_constraints t JOIN information_schema.key_column_usage k USING (constraint_name,table_schema,table_name) WHERE t.constraint_type='PRIMARY KEY' AND t.table_schema='db' AND t.table_name=tbl'
6. 查看你的數庫有多大
復制代碼 代碼如下:
ELECT table_schema AS 'Db Name', Round( Sum( data_length + index_length ) / 1024 / 1024, 3 ) AS 'Db Size (MB)', Round( Sum( data_free ) / 1024 / 1024, 3 ) AS 'Free Space (MB)' FROM information_schema.tables GROUP BY table_schema ;
