数据库表添加新字段(支持重复执行)

DECLARE 
    COLEXIST NUMBER;   
BEGIN 
   SELECT COUNT(1) INTO COLEXIST FROM USER_TAB_COLUMNS WHERE TABLE_NAME=UPPER(‘HISTORY‘) AND COLUMN_NAME=UPPER(‘NAME‘);--判断列是否存在
   IF COLEXIST = 0  THEN  --如果不存在，进行创建
      EXECUTE IMMEDIATE  
              ‘ALTER TABLE HISTORY ADD NAME VARCHAR(64) DEFAULT (‘‘ ‘‘) NOT NULL‘;
    END IF ;   
END;
/  

DELIMITER ;;
DROP PROCEDURE IF EXISTS COLUMNADD; 
CREATE DEFINER=`root`@`%` PROCEDURE `COLUMNADD`(TBNAME VARCHAR(30),COLNAME VARCHAR(32),COLTYPE VARCHAR(64))
BEGIN
DECLARE  P_STR VARCHAR(300);
IF NOT EXISTS (SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME = TBNAME AND COLUMN_NAME =COLNAME) THEN  -- 判断列是否存在
   SET P_STR= CONCAT(‘ALTER TABLE ‘,TBNAME,‘ ADD ‘,COLNAME ,‘ ‘,COLTYPE); 
   SET @SQL = P_STR;
   PREPARE STMT FROM @SQL;
   EXECUTE STMT;
   DEALLOCATE PREPARE STMT;
END IF; 
END;;
DELIMITER ;

-- 调用该存储过程
CALL COLUMNADD(‘LF_WCD_P1‘,‘WCD_URLP1‘,‘VARCHAR(64) NOT NULL DEFAULT ‘‘‘‘‘);