如何从另一个表中查找字段名的表中选择一个字段？

Question

Doing some ETL and I have a wide file with lots of cols, for each different value. I am trying to transform this into a vertical text file with one row per value item. So my data table looks like;

Store  Date  Col1 Col2 Col3 ...
Store1 1/2/12 12   23   34  ...
Store2 1/2/12 23   34   35  ...

My Col lookup table looks like;

GLCode GLDesc TaxRate XLSColName
00.1234 Cash  0.00    Col2 

So in my output file line I need;
Store1,1/2/34,00.1234,0.00,23
where 23 is the value from the Data table in the Col2 field which was specificed in teh GL Lookup field.

I have been trying to do this is SQL as part of an SSIS package, as I could not see how to do it with the Lookup task, but cannot seem to do it in SQL either !!

Hope that makes sense and thanks for your help ! JK

Answer 1

From your what I understand of your question, you're looking for the SQL Server UNPIVOT function , which takes columns and pivots them into individual rows/values. Combine that with a join to get your required information from the Lookup table.

To do this in SSIS, you could use the UNPIVOT Transformation

Answer 2

You will need to look at pivoting the data table from:

Store  Date  Col1 Col2 Col3 ...
Store1 1/2/12 12   23   34  ...
Store2 1/2/12 23   34   35  ...

Store  Date  Col Value
Store1 1/2/12 Col1 12
Store1 1/2/12 Col2 23
Store1 1/2/12 Col3 34
Store2 1/2/12 Col1 23
Store2 1/2/12 Col2 34
Store2 1/2/12 Col3 35

So you can treat the column name as data to be joined/looked up.

Answer 3

Your question is a little confusing. I understand what you are trying to do but not 100% sure where the data is stored. Is this correct?: You have 2 tables, 1 table has the data you want? 1 table has the value to search the first table for?

If so you want something like:

SELECT t1.col1, t1.col2, ... 
FROM table_1 t1 
    LEFT JOIN table_2 t2 ON t1.common_field = t2.common_field 
WHERE t2.search_by = 'CRITERIA'