Check the existence of Entities and their structure in SQL Server

1. Check If Column Exists in Table:
IF EXISTS(SELECT 1 FROM sys.columns
          WHERE Name = N'columnName'
          AND Object_ID = Object_ID(N'schemaName.tableName'))
BEGIN
    -- Column Exists
END


2. Check If Table Exists
IF EXISTS (SELECT * FROM INFORMATION_SCHEMA.TABLES
           WHERE TABLE_NAME = N'Customers')
BEGIN
  PRINT 'Table Exists'
END


3. Check If Stored Procedure Exists in SQL
IF EXISTS ( SELECT *
            FROM   sysobjects
            WHERE  id = object_id(N'[dbo].[MyProc]')
                   and OBJECTPROPERTY(id, N'IsProcedure') = 1 )
BEGIN
    --DROP PROCEDURE [dbo].[MyProc]
END

4. Check If User-Defined Function Exists in SQL
IF EXISTS (SELECT *
           FROM   sys.objects
           WHERE  object_id = OBJECT_ID(N'[dbo].[foo]')
                  AND type IN ( N'FN', N'IF', N'TF', N'FS', N'FT' ))
Begin
  --DROP FUNCTION [dbo].[foo]
End

GO