Background

I recently wrote an EF Core migration which included dropping an index. This index was somewhat unusual, as it didn’t follow our naming conventions and we didn’t know how it had been added. The disparity in naming suggested it may have been manually added on a database, and might not necessarily be on all databases which are in use across all environments.

Prompted by a very helpful comment in a code review, I wanted to check a number of test databases to see which of them had the index in question. Given the number of databases which needed checking, I wanted to avoid manually checking them all. The obvious solution was to have a SQL script do the work for me.

SQL Script

I asked GitHub Copilot to create a script for me, then modified it myself until I was happy with it. This is the SQL script I used. Although I was happy with how it ran, if you plan to use this then please do check this SQL does what you expect before running it on your own databases.

-- Set these when running the script
DECLARE @SchemaName NVARCHAR(255) = 'TODO'
DECLARE @TableName NVARCHAR(255) = 'TODO'
DECLARE @IndexName NVARCHAR(255) = 'TODO'

-- Leave these for the script to use
DECLARE @DatabaseName NVARCHAR(255)
DECLARE @SQL NVARCHAR(MAX)

-- Create a table to store the results
CREATE TABLE #IndexCheckResults
(
    DatabaseName NVARCHAR(255),
    IndexExists  BIT
)

-- Cursor to iterate through all databases
DECLARE db_cursor CURSOR FOR
SELECT
    name
FROM sys.databases
WHERE state_desc = 'ONLINE'
  AND name NOT IN ('master', 'tempdb', 'model', 'msdb')

OPEN db_cursor
FETCH NEXT
FROM db_cursor
INTO @DatabaseName

WHILE @@FETCH_STATUS = 0
BEGIN
    -- Dynamic SQL to check for the index in the current database
    SET
    @SQL = '
    IF EXISTS (
        SELECT 1
        FROM [' + @DatabaseName + '].sys.indexes
        WHERE name = ''' + @IndexName + '''
        AND object_id = OBJECT_ID(''[' + @DatabaseName + '].' + @SchemaName + '.' + @TableName + ''')
    )
    BEGIN
        INSERT INTO #IndexCheckResults (DatabaseName, IndexExists)
        VALUES (''' + @DatabaseName + ''', 1)
    END
    ELSE
    BEGIN
        INSERT INTO #IndexCheckResults (DatabaseName, IndexExists)
        VALUES (''' + @DatabaseName + ''', 0)
    END'

    EXEC sp_executesql @SQL

    FETCH NEXT FROM db_cursor INTO @DatabaseName
END

CLOSE db_cursor 
DEALLOCATE db_cursor

-- Select the results
SELECT *
FROM #IndexCheckResults

-- Drop the temporary table
DROP TABLE #IndexCheckResults

Output

The output is a table containing a list of databases, with a boolean column indicating whether or not the index exists in each database. It ran near-enough instantaneously and gave me exactly the information I needed to have confidence that my migration would run without problems on all of our environments.

SQL to check if an index exists across multiple databases

Background

SQL Script

Output