如何在SQL中的IF EXISTS中使用AND条件？

IF EXISTS(SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'X' AND COLUMN_NAME = 'Y') 

IF EXISTS(SELECT * FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = 'Z' AND COLUMN_NAME = 'A')
BEGIN
    UPDATE [dbo].[X] 
        SET Y= (SELECT inst.[A] FROM [dbo].[Z] s WHERE s.[B] = [dbo].[x].[B]);
END    
    GO
IF EXISTS(SELECT * FROM INFORMATION_SCHEMA.COLU