mysql中concat函数的用法

SELECT CONCAT('MySQL', '字符串', '函数') AS str;

str           |

--------------+

MySQL字符串函数|

SELECT CONCAT('MySQL', NULL, '函数') AS str;

str|

---+

   |

SELECT 'MySQL' '字符串' '函数' AS str;

str           |

--------------+

MySQL字符串函数|