mysql sql-syntax-prepared-statements 变量做表名 字符函数

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  参考语法 http://dev.mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html

sql 片段 记录下

DELIMITER $$USE `portal_group`$$DROP PROCEDURE IF EXISTS `proc_sync_data`$$CREATE DEFINER=`root`@`%` PROCEDURE `proc_sync_data`()SQL SECURITY INVOKERBEGINDECLARE cur2_tag CURSOR FOR SELECT id ,entity_name,data_from,data_to FROM sync_table WHERE data_from = 'group';DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done_cursor = 1 ; OPEN cur2_tag;  SET done_cursor = 0;FETCH cur2_tag INTO var_id,var_entity_name,var_data_from,var_data_to;WHILE (done_cursor  = 0) DOBEGIN   IF (fc_sync_data(var_entity,var_data_from_db)='1') THENSET @execSql = CONCAT('select count(*) into @records  from ',var_data_from_db_table,';'); -- 变量 做 表名PREPARE stmt1 FROM @execSql;EXECUTE stmt1;DEALLOCATE PREPARE stmt1; SET num = @records;  -- 从结果中获取 执行的记录数IF (num>0) THENSET @execSql = CONCAT('truncate table ',var_data_to_db_table,';'); -- 变量 做 表名 PREPARE stmt1 FROM @execSql;  EXECUTE stmt1;SET @execSql = CONCAT('INSERT INTO ',var_data_to_db_table ,' SELECT * FROM ',var_data_from_db_table,';');PREPARE stmt1 FROM @execSql;  EXECUTE stmt1;END IF;END IF;END;SET done_cursor = 0 ;		FETCH cur2_tag INTO var_id,var_entity_name,var_data_from,var_data_to;END WHILE;CLOSE cur2_tag;END$$DELIMITER ;

字符函数        http://tool.oschina.net/apidocs/apidoc?api=mysql-5.1-zh    12. 函数和操作符

-- mysql 字符串函数
-- 去空格
SELECT LENGTH(TRIM('    123456    '))
6
-- 索引每个字符时 会用到 大小写 
SELECT ASCII('a')<ASCII('z')
1
SELECT ASCII('Z'); 90
SELECT ASCII('A'); 65SELECT ASCII('a'); 97
SELECT ASCII('z'); 122
-- 替换函数
SELECT REPLACE('ABCDEFGHC','C','123') 
AB123DEFGH123
-- 截取 
SELECT SUBSTRING('1234567890',5,1)
5
SELECT SUBSTRING('1234567890',-5,1)
6

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