-- View field attributes of tables in the database
SELECT COLUMN_NAME column name, COLUMN_COMMENT name, COLUMN_TYPE data type, IF(COLUMN_KEY='PRI', "primary key", "non-primary key") primary key,
IF(IS_NULLABLE='NO', "Can be empty", "not empty") is empty, "" secondary comment, COLUMN_DEFAULT default value, TABLE_SCHEMA database name,
DATA_TYPE field type, CHARACTER_MAXIMUM_LENGTH length FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA = 'DatabaseName'
--删除数据
DELETE A FROM SYS_USER_ROLE A WHERE NOT EXISTS (SELECT 1 FROM SYS_USER B WHERE A.USER_ID = B.ID)
--Delete data, delete the same table and report an error
DELETE FROM JIANGSU_AB01 WHERE AAB004 IN (SELECT * FROM (SELECT B.AAB004 FROM JIANGSU_AB01 B GROUP BY B.AAB004 HAVING COUNT(1) > 1) B)
-- Set GROUP_CONCAT() function splicing length
SET SESSION GROUP_CONCAT_MAX_LEN = 1024;
-- Convert one column and multiple rows of a table field into a string
SELECT GROUP_CONCAT(CONCAT(' AS "', UPPER(COLUMN_NAME), '"') SEPARATOR ', ') COL2ROW FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_NAME = 'TableName' AND TABLE_SCHEMA = 'DatabaseName';
-- 去除空格
UPDATE JIANGSU_AB01 SET AAB031 = TRIM(REPLACE(REPLACE(REPLACE(REPLACE(AAB031, CHAR(10), ''), CHAR(13), ''), '-', ''), ' ', ''));
SHOW VARIABLES LIKE 'event_scheduler';
SELECT * FROM MYSQL.EVENT;
SHOW VARIABLES LIKE '%TIME%';
SET GLOBAL EVENT_SCHEDULER = ON;
SET TIME_ZONE = '+8:00';
SET SYSTEM_TIME_ZONE = '+8:00';
Open the database FEDERATED function to create a table similar to ORACLE's DBLINK ( CREATE TABLE TABLE_NAME(...) ENGINE = FEDERATED CONNECTION='mysql://[username]:[password]@[location]:[port]/[ db-name]/[table-name] to be tested)
-- 重复数据设置成1
UPDATE TableName SET COLUMNNAME ='1' WHERE COLUMNNAME IN (SELECT COLUMNNAME FROM (SELECT COLUMNNAME , COUNT(1) FROM TableName GROUP BY COLUMNNAME HAVING COUNT(1) > 1) A)