SQL - 将具有默认值的新列添加到DB中的所有表

Question

I have the following statement:

EXEC sp_MSforeachtable '
    DECLARE @defaultId integer;
    SET @defaultId = 13;

    IF EXISTS(SELECT name FROM sys.sysobjects WHERE Name = N''?'' AND xtype = N''U'')
    BEGIN   
        IF COL_LENGTH(''[?]'',''NewColumn'') IS NULL
        BEGIN
            ALTER TABLE [?] ADD NewColumn integer null
            UPDATE [?]
            SET NewColumn = @defaultId
        END
    END
'

I'm trying to add NewColumn column to all the tables in my DB that don't have it and set the default value to 13 . I execute it and it says it completed successfully, but nothing has changed. What am I doing wrong here?

---

Note: I got a table called User hence the "[]" . I don't know if this adds extra complexity to it.

Answer 1

I don't particulary like debugging sp_MSforeachtable code so I suggest you this method:

DECLARE @Name AS VARCHAR(128)

DECLARE C_Table CURSOR FOR
    SELECT sys.objects.Name
    FROM sys.objects
    WHERE sys.objects.type = 'U' AND
        sys.objects.Name NOT IN (
            SELECT DISTINCT sys.objects.Name
            FROM sys.objects INNER JOIN
            sys.columns ON sys.objects.object_id = sys.columns.object_id 
            WHERE sys.objects.type = 'U' AND
                sys.columns.Name = 'NewColumn'
        )

OPEN C_Table
FETCH NEXT FROM C_Table INTO @Name

WHILE @@FETCH_STATUS = 0
BEGIN

    EXEC('ALTER TABLE ' + @Name + ' ADD NewColumn INTEGER NULL')
    EXEC('ALTER TABLE ' + @Name + ' ADD CONSTRAINT DF_' + @Name + '_A DEFAULT 13 FOR NewColumn')
    EXEC('UPDATE ' + @Name + ' SET NewColumn = 13')

    FETCH NEXT FROM C_Table INTO @Name

END

CLOSE C_Table
DEALLOCATE C_Table

This is an alternative solution using sp_MSforeachtable and your syntax; please note that:

• you need to PARSENAME the name provided by sp_MSforeachtable (ie [yourschema].[yourtable] ) because sys.objects.name contains only table name (ie: yourtable )
• you have to use 2 step because it seems that is not possible to use GO inside a sp_MSforeachtable
• you can't use variable in ALTER TABLE but you must specify a fixed DEFAULT

This is the code:

EXEC sp_MSforeachtable '

    IF EXISTS(SELECT * FROM sys.sysobjects WHERE Name = PARSENAME(''?'', 1) AND xtype = N''U'')
    BEGIN   
        IF COL_LENGTH(PARSENAME(''?'', 1), ''NewColumn'') IS NULL
        BEGIN
            ALTER TABLE ? ADD NewColumn INT NULL DEFAULT(13)
        END
    END

'

EXEC sp_MSforeachtable '

    DECLARE @defaultId INT
    SELECT @defaultId = 13

    IF EXISTS(SELECT * FROM sys.sysobjects WHERE Name = PARSENAME(''?'', 1) AND xtype = N''U'')
    BEGIN   
        IF NOT COL_LENGTH(''?'', ''NewColumn'') IS NULL
        BEGIN
            UPDATE ? SET NewColumn = @defaultId
        END
    END

'

Answer 2

Most likely that NewColumn is not recognized. try

EXEC sp_MSforeachtable '
DECLARE @defaultId integer;
SET @defaultId = 13;
IF EXISTS(SELECT name FROM sys.sysobjects WHERE Name = PARSENAME(''?'',1) AND xtype = N''U'')
BEGIN   
    IF COL_LENGTH(''?'',''NewColumn'') IS NULL
    BEGIN
        ALTER TABLE ? ADD NewColumn integer null
        EXEC(CONCAT(''UPDATE ? SET NewColumn = '', @defaultId))
    END
END'

Answer 3

You need to do this in two steps.

The update statement is evaluated before execution and will throw an error (as there is no column at this moment)

Step 1 (alter table):

EXEC sp_MSforeachtable '

IF EXISTS(SELECT * FROM sys.sysobjects WHERE Name = parsename(N''?'', 1) AND xtype = N''U'')
BEGIN   
    IF COL_LENGTH(''[?]'',''NewColumn'') IS NULL
    BEGIN
        ALTER TABLE [?] ADD NewColumn integer null
    END
END
'

Step 2 (set value):

EXEC sp_MSforeachtable '
DECLARE @defaultId integer;
SET @defaultId = 13;

IF EXISTS (SELECT * FROM sys.sysobjects WHERE Name = parsename(N''?'', 1) AND xtype = N''U'')
BEGIN   
    IF COL_LENGTH(''[?]'',''NewColumn'') IS not NULL
    BEGIN
        UPDATE [?]
        SET NewColumn = @defaultId
    END
END
'

You mentioned a default value. You only updated the values of the new column with a fixed value without defining a default. This might be an difference although not important for this issue.