sql_CONCAT拼接SUBSTR截取

CONCAT和SUBSTR不一样的数据库有不一样的语法。

（1）CONCAT

MySQL: CONCAT( )

Oracle: CONCAT( ), ||

SQL Server: +

（2）SUBSTR

MySQL: SUBSTR( ), SUBSTRING( )

Oracle: SUBSTR( )

SQL Server: SUBSTRING( )

（3）具体用法如例：

SELECT CONCAT (Region_Name, Store_Name) FROM Geography  WHERE Store_Name = 'Boston';

查询结果：EastBoston

SELECT Region_Name || ' ' || Store_Name FROM Geography  WHERE Store_Name = 'Boston';

查询结果：East Boston

SELECT Region_Name + ' ' + Store_Name FROM Geography WHERE Store_Name = 'Boston';

查询结果：East Boston

SELECT SUBSTR (Store_Name, 3) FROM Geography WHERE Store_Name = 'Los Angeles';

查询结果：s Angeles

SELECT SUBSTR (Store_Name, 2, 4) FROM Geography WHERE Store_Name = 'San Diego';

查询结果：an D