How do I query if a database schema exists - sql-server-2005

Question

As part of our build process we run a database update script as we deploy code to 4 different environments. Further, since the same query will get added to until we drop a release into production it has to be able to run multiple times on a given database. Like this:
IF NOT EXISTS (SELECT * FROM sys.tables WHERE object_id = OBJECT_ID(N'[Table]'))
BEGIN
CREATE TABLE [Table]
(...)
END
Currently I have a create schema statement in the deployment/build script. Where do I query for the existence of a schema?

Answer 1

Are you looking for sys.schemas?
IF NOT EXISTS (SELECT * FROM sys.schemas WHERE name = 'jim')
BEGIN
EXEC('CREATE SCHEMA jim')
END
Note that the CREATE SCHEMA must be run in its own batch (per the answer below)

Answer 2

#bdukes is right on the money for determining if the schema exists, but the statement above won't work in SQL Server 2005. CREATE SCHEMA <name> needs to run in its own batch. A work around is to execute the CREATE SCHEMA statement in an exec.
Here is what I used in my build scripts:
IF NOT EXISTS (SELECT 1 FROM sys.schemas WHERE name = '<name>')
BEGIN
-- The schema must be run in its own batch!
EXEC( 'CREATE SCHEMA <name>' );
END

Answer 3

This is old so I feel compelled to add: For SQL SERVER 2008+ These all work (for the select part), then use EXECUTE('CREATE SCHEMA <name>') to actually create it on negative results.
DECLARE #schemaName sysname = 'myfunschema';
-- shortest
If EXISTS (SELECT 1 WHERE SCHEMA_ID(#schemaName) IS NOT NULL)
PRINT 'YEA'
ELSE
PRINT 'NOPE'
SELECT DB_NAME() AS dbname WHERE SCHEMA_ID(#schemaName) IS NOT NULL -- nothing returned if not there
IF NOT EXISTS ( SELECT top 1 *
FROM sys.schemas
WHERE name = #schemaName )
PRINT 'WOOPS MISSING'
ELSE
PRINT 'Has Schema'
SELECT SCHEMA_NAME(SCHEMA_ID(#schemaName)) AS SchemaName1 -- null if not there otherwise schema name returned
SELECT SCHEMA_ID(#schemaName) AS SchemaID1-- null if not there otherwise schema id returned
IF EXISTS (
SELECT sd.SchemaExists
FROM (
SELECT
CASE
WHEN SCHEMA_ID(#schemaName) IS NULL THEN 0
WHEN SCHEMA_ID(#schemaName) IS NOT NULL THEN 1
ELSE 0
END AS SchemaExists
) AS sd
WHERE sd.SchemaExists = 1
)
BEGIN
SELECT 'Got it';
END
ELSE
BEGIN
SELECT 'Schema Missing';
END

Answer 4

If the layout of components allows it, this works too.
IF EXISTS (SELECT 1 FROM sys.schemas WHERE name = 'myschema') SET NOEXEC ON
go
CREATE SCHEMA myschema
GO
SET NOEXEC OFF -- if any further processing is needed.
GO

Answer 5

Just to be extra "defensive", the following version generates a Type conversion error to account for the possibility (however unlikely) of > 1 matching Schema's similar to how validation code often intentionally Throw Exception's because I believe it's good to and I believe it's "'best practice'" to account for all possible return results however unlikely and even if it's just to generate a fatal exception because the known effects of stopping processing is usually better than unknown cascading effects of un-trapped errors. Because it's highly unlikely, I didn't think it's worth the trouble of a separate Count check + Throw or Try-Catch-Throw to generate a more user-friendly fatal error but still fatal error nonetheless.
SS 2005-:
declare #HasSchemaX bit
set #HasSchemaX = case (select count(1) from sys.schemas where lower(name) = lower('SchemaX')) when 1 then 1 when 0 then 0 else 'ERROR' end
SS 2008+:
declare #HasSchemaX bit = case (select count(1) from sys.schemas where lower(name) = lower('SchemaX')) when 1 then 1 when 0 then 0 else 'ERROR' end
Then:
if #HasSchemaX = 1
begin
...
end -- if #HasSchemaX = 1

Answer 6

IF NOT EXISTS (SELECT TOP (1) 1 FROM [sys].[schemas] WHERE [name] = 'Person')
BEGIN
EXEC ('CREATE SCHEMA [Person]')
END
IF NOT EXISTS (SELECT TOP (1) 1 FROM [sys].[tables] AS T
INNER JOIN [sys].[schemas] AS S ON S.schema_id = T.schema_id
WHERE T.[name] = 'Guests' AND S.[name] = 'Person')
BEGIN
EXEC ('CREATE TABLE [Person].[Guests]
(
[GuestId] INT IDENTITY(1, 1) NOT NULL,
[Forename] NVARCHAR(100) NOT NULL,
[Surname] NVARCHAR(100) NOT NULL,
[Email] VARCHAR(255) NOT NULL,
[BirthDate] DATETIME2 NULL,
CONSTRAINT [PK_Guests_GuestId] PRIMARY KEY CLUSTERED ([GuestId]),
CONSTRAINT [UX_Guests_Email] UNIQUE([Email])
)')
END
NOTICE: CREATE SCHEMA AND CREATE TABLE NEED COMPLETLY SEPARATED BATCH TO EXECUTE
TO MORE DESCRIPTION VISIT MICROSOFT DOCS WEBSITE :)

Answer 7

As of SQL Server 2005 version 9.0 you can use the INFORMATION_SCHEMA.SCHEMATA view to check if the schema exists:
IF NOT EXISTS (
SELECT SCHEMA_NAME
FROM INFORMATION_SCHEMA.SCHEMATA
WHERE SCHEMA_NAME = '<schema name>' )
BEGIN
EXEC sp_executesql N'CREATE SCHEMA <schema name>'
END
GO
INFORMATION_SCHEMA views are the ISO standard and are generally preferable; these were adopted to make the syntax more consistent across different SQL database platforms.
Note that the CREATE SCHEMA must be run in its own batch