sql中的concat（）将如何添加两个或多个包含特殊字符的参数？

Question

select CONCAT(address,city) as Address from student order by Address desc;

This is a query to display the address and the city with an alias name as Address from a student table

--- Program output ---

ADDRESS
----------------------------------------------------------------------
LMCCoimbatore
FFFVilupuram
BBBAgra
ABCSalem
AAAPondichery


--- Expected output (text)---
ADDRESS
------------------------------------------------------------------------
LMC, Coimbatore
FFF, Vilupuram
BBB, Agra
ABC, Salem
AAA, Pondichery

how can i add the coma and space between the city and address? when i use the third string as ', ' it is giving an invalid number of arguments error.

Answer 1

CONCAT versions:

I would recommend CONCAT since it will protect you from returning NULL when one of arguments is null - at least in MSSQL.

MSSQL & MySQL & PostgresSQL & Teradata:

select CONCAT(address,', ',city) as Address from student order by Address desc;

MySQL version 2:

select CONCAT_WS(', ', address,city) as Address from student order by Address desc;

Oracle & IBM DB2 & IBM Informix:

select CONCAT(address,CONCAT(', ',city)) as Address from student order by Address desc;

IBM DB2:

select address CONCAT ', ' CONCAT city as Address from student order by Address desc;

Non-CONCAT versions:

|| is ANSI standard, however not all systems use it.

MSSQL & Sybase IQ:

select address + ', ' + city as Address from student order by Address desc;

MySQL (so called proximity operator, default behavior):

select address ', ' city as Address from student order by Address desc;

PostgresSQL & Oracle & MySQL (with SET sql_mode='PIPES_AS_CONCAT'; ) & IBM Informix & Sybase IQ:

select address || ', ' || city as Address from student order by Address desc;

Answer 2

In addition to the other answers, I'd like to mention that the standard (ISO 9075) concatenation operator in SQL is || but it isn't supported by all DB engines.

select address || ', ' || city

Oracle uses this one