在表中将所有列设置为“null”

Question

Is there a quick way to change all fields in a table that are null to just empty fields. I have many columns so wondered if there was a way to do it by table rather than column by column.

I need something like

update table 1 
set * = '' 
where * is null

but obviously this is incorrect syntax

Answer 1

This code will generate update statements list, you have to only run it:

SELECT  'update '+ so.name+' set '+sc.name+'= '''' where '+sc.name+' is null '   
FROM sysobjects so
JOIN syscolumns sc ON so.id = sc.id
JOIN systypes st ON sc.xtype=st.xtype  
where so.type = 'U'
and st.name in('varchar','char')
--and so.name = 'tab' <--- if you need update only one table

Here (sql fiddle) you can see how it works.

Answer 2

If you want to generate a script that will update all of the NULLable fields that contain NULLs to blanks, you can use the following code:

DECLARE @TAB VARCHAR(1000) = 'ProductVendor', 
        @COL VARCHAR(1000), 
        @SQL VARCHAR(MAX) 
DECLARE UPDATE_CURSOR CURSOR LOCAL FAST_FORWARD FOR 
  SELECT t2.NAME 
    FROM (SELECT * 
            FROM SYSOBJECTS 
           WHERE XTYPE = 'u' 
                 AND NAME = @TAB)T1 
         INNER JOIN SYSCOLUMNS t2 
                 ON T1.ID = t2.ID 
   WHERE t2.ISNULLABLE = 1 

OPEN UPDATE_CURSOR 

SET @SQL = 'UPDATE ' + @TAB + ' SET ' 

FETCH NEXT FROM UPDATE_CURSOR INTO @COL 

WHILE @@FETCH_STATUS = 0 
  BEGIN 
      SET @SQL = @SQL + @COL + ' = Isnull(' + @COL + ', ''''),' 

      FETCH NEXT FROM UPDATE_CURSOR INTO @COL 
  END 

CLOSE UPDATE_CURSOR 

DEALLOCATE UPDATE_CURSOR 

SET @SQL = LEFT(@SQL, Len(@SQL) - 1) 

EXEC (@SQL) 

All you need to do is change the table name at the beginning (the TAB variable). The script generates a single query that will update all of the columns in one run.

Answer 3

试试这个

 update table1 set columnnames='' where columnnames ='null'

Answer 4

Try something like this:

UPDATE TABLE1 
   SET ( COL1, COL2, COL3, COL4 ) = (SELECT COL1A, 
                                            COL2A, 
                                            COL3A, 
                                            COL4A 
                                       FROM TABLE2 
                                      WHERE COL5A = TABLE1.COL5) 
 WHERE COL5 IN (SELECT COL5A 
                  FROM TABLE2)