[sql-server] Change collations of all columns of all tables in SQL Server

Using the cursor based variations above as a starting point, the script below will just output a set of UPDATE statements to set to DATABASE_DEFAULT, it won't actually do the UPDATES.

It supports schema, the full set of char and text types and retains the existing NULL / NOT NULL.

I plan to use the output to find to statements that fail in a lower environment and then manually adapt the resulting script to drop and recreate the constraints as needed.

DECLARE @collate nvarchar(100);
DECLARE @schema nvarchar(255);
DECLARE @table nvarchar(255);
DECLARE @column_name nvarchar(255);
DECLARE @column_id int;
DECLARE @data_type nvarchar(255);
DECLARE @max_length int;
DECLARE @max_length_str nvarchar(100);
DECLARE @is_nullable bit;
DECLARE @row_id int;
DECLARE @sql nvarchar(max);
DECLARE @sql_column nvarchar(max);

SET @collate = 'DATABASE_DEFAULT';

DECLARE local_table_cursor CURSOR FOR

SELECT (s.[name])schemaName, (o.[name])[tableName]
FROM sysobjects sy 
INNER JOIN sys.objects  o on o.name = sy.name
INNER JOIN sys.schemas s ON o.schema_id = s.schema_id
WHERE OBJECTPROPERTY(sy.id, N'IsUserTable') = 1
ORDER BY s.[name], o.[name]

OPEN local_table_cursor FETCH NEXT FROM local_table_cursor INTO @schema,@table

WHILE @@FETCH_STATUS = 0
BEGIN
    DECLARE local_change_cursor CURSOR FOR

    SELECT ROW_NUMBER() OVER (ORDER BY c.column_id) AS row_id
        , c.name column_name
        , t.Name data_type
        , col.CHARACTER_MAXIMUM_LENGTH
        , c.column_id
        , c.is_nullable
    FROM sys.columns c
    JOIN sys.types t ON c.system_type_id = t.system_type_id
    JOIN INFORMATION_SCHEMA.COLUMNS col on col.COLUMN_NAME = c.name and c.object_id = OBJECT_ID(col.TABLE_NAME)
    LEFT OUTER JOIN sys.index_columns ic ON ic.object_id = c.object_id AND ic.column_id = c.column_id
    LEFT OUTER JOIN sys.indexes i ON ic.object_id = i.object_id AND ic.index_id = i.index_id
    WHERE c.object_id = OBJECT_ID(@schema+'.'+@table) AND (t.Name LIKE '%char%' OR t.Name LIKE '%text%') 
    ORDER BY c.column_id

    OPEN local_change_cursor
    FETCH NEXT FROM local_change_cursor
    INTO @row_id, @column_name, @data_type, @max_length, @column_id, @is_nullable

    WHILE @@FETCH_STATUS = 0
    BEGIN

        SET @max_length_str = @max_length
        IF (@max_length = -1) SET @max_length_str = 'max'
        IF (@max_length > 4000) SET @max_length_str = '4000'

        SET @sql =
        CASE 
            WHEN @data_type like '%text%' 
            THEN 'ALTER TABLE [' + @schema+ '].['+ @table + '] ALTER COLUMN [' + @column_name + '] ' + @data_type + ' COLLATE ' + @collate + ' ' + CASE WHEN @is_nullable = 0 THEN 'NOT NULL' ELSE 'NULL' END
            ELSE 'ALTER TABLE [' + @schema+ '].['+ @table + '] ALTER COLUMN [' + @column_name + '] ' + @data_type + '(' + @max_length_str + ') COLLATE ' + @collate + ' ' + CASE WHEN @is_nullable = 0 THEN 'NOT NULL' ELSE 'NULL' END
        END
        PRINT @sql

        FETCH NEXT FROM local_change_cursor
        INTO @row_id, @column_name, @data_type, @max_length, @column_id, @is_nullable

    END

    CLOSE local_change_cursor
    DEALLOCATE local_change_cursor

    FETCH NEXT FROM local_table_cursor
    INTO @schema, @table
END

CLOSE local_table_cursor
DEALLOCATE local_table_cursor
GO