How to find out whether a table has some unique columns

Question

I use MS SQL Server.

Ive been handed some large tables with no constrains on them, no keys no nothing.

I know some of the columns have unique values. Is ther

Answer 1

A few words what my code does:

1. Read's all tables and columns

2. Creates a temp table to hold table/columns with duplicate keys

3. For each table/column it runs a query. If it finds a count(*)>1 for at least one value it makes an insert into the temp table

4. Select's column and values from the system tables that do not match table/columns that are found to have duplicates

   DECLARE @sql VARCHAR(max)
   DECLARE @table VARCHAR(100)
   DECLARE @column VARCHAR(100)
   
   
   CREATE TABLE #temp (tname VARCHAR(100),cname VARCHAR(100))
   
   DECLARE mycursor CURSOR FOR
   select t.name,c.name
   from sys.tables t
   join sys.columns c on t.object_id = c.object_id
   where system_type_id not in (34,35,99)
   
   OPEN mycursor
   FETCH NEXT FROM mycursor INTO @table,@column
   
   WHILE @@FETCH_STATUS = 0
   BEGIN
   SET @sql = 'INSERT INTO #temp SELECT DISTINCT '''+@table+''','''+@column+ ''' FROM ' + @table + ' GROUP BY ' + @column +' HAVING COUNT(*)>1 '
   EXEC (@sql)
   FETCH NEXT FROM mycursor INTO @table,@column
   END
   
   select t.name,c.name
   from sys.tables t
   join sys.columns c on t.object_id = c.object_id
   left join #temp on t.name = #temp.tname and c.name = #temp.cname
   where system_type_id not in (34,35,99) and #temp.tname IS NULL
   
   DROP TABLE #temp
   
   CLOSE mycursor
   DEALLOCATE mycursor