Проверить, существует ли индекс

if exists(
  SELECT *
  FROM sysobjects o 
  INNER JOIN sysindexes i 
     ON o.id = i.id
  WHERE o.xtype = 'U' AND 
        i.indid > 0 AND 
        i.indid < 255 AND 
        INDEXPROPERTY(i.id, @IndexName, 'isStatistics') = 0 AND 
        o.name = @TableName)
  Set @exists=1
else
  Set @exists=0