SQL Server: Best way to concatenate multiple columns?

问题

I am trying to concatenate multiple columns in a query in SQL Server 11.00.3393.

I tried the new function CONCAT() but it's not working when I use more than two columns.

So I wonder if that's the best way to solve the problem:

SELECT CONCAT(CONCAT(CONCAT(COLUMN1,COLUMN2),COLUMN3),COLUMN4) FROM myTable

I can't use COLUMN1 + COLUMN2 because of NULL values.

EDIT

If I try SELECT CONCAT('1','2','3') AS RESULT I get an error

The CONCAT function requires 2 argument(s)

回答1:

Through discourse it's clear that the problem lies in using VS2010 to write the query, as it uses the canonical CONCAT() function which is limited to 2 parameters. There's probably a way to change that, but I'm not aware of it.

An alternative:

SELECT '1'+'2'+'3'

This approach requires non-string values to be cast/converted to strings, as well as NULL handling via ISNULL() or COALESCE():

SELECT  ISNULL(CAST(Col1 AS VARCHAR(50)),'')
      + COALESCE(CONVERT(VARCHAR(50),Col2),'')

回答2:

SELECT CONCAT(LOWER(LAST_NAME), UPPER(LAST_NAME)
       INITCAP(LAST_NAME), HIRE DATE AS ‘up_low_init_hdate’)
FROM EMPLOYEES
WHERE HIRE DATE = 1995

回答3:

Try using below:

SELECT 
    (RTRIM(LTRIM(col_1))) + (RTRIM(LTRIM(col_2))) AS Col_newname,
    col_1,
    col_2 
FROM 
    s_cols 
WHERE
    col_any_condition = ''
;

回答4:

Blockquote

Using concatenation in Oracle SQL is very easy and interesting. But don't know much about MS-SQL.

Blockquote

Here we go for Oracle : Syntax: SQL> select First_name||Last_Name as Employee from employees;

Result: EMPLOYEE

EllenAbel SundarAnde MozheAtkinson

Here AS: keyword used as alias. We can concatenate with NULL values. e.g. : columnm1||Null

Suppose any of your columns contains a NULL value then the result will show only the value of that column which has value.

You can also use literal character string in concatenation.

e.g. select column1||' is a '||column2 from tableName; Result: column1 is a column2. in between literal should be encolsed in single quotation. you cna exclude numbers.

NOTE: This is only for oracle server//SQL.

回答5:

If the fields are nullable, then you'll have to handle those nulls. Remember that null is contagious, and concat('foo', null) simply results in NULL as well:

SELECT CONCAT(ISNULL(column1, ''),ISNULL(column2,'')) etc...

Basically test each field for nullness, and replace with an empty string if so.

来源：https://stackoverflow.com/questions/24371044/sql-server-best-way-to-concatenate-multiple-columns

标签

sql

sql-server-2012