In Concatenate and NoConcatenate in QlikView – Part 1 you saw how automatic concatenation occurs in QlikView.
In this Part 2, you will see Forced Concatenation and how to prevent Concatenation i.e. NoConcatenation.
If two or more tables do not have exactly same name and number of fields, it is still possible to concatenate them by using
concatenate keyword before the load statement.
Let us load 2 tables with different sets of fields
Now to force concatenation use Concatenate key word before the load of second table
Observe that the tables are concatenated and numbers of rows is 7 i.e. Sum of rows in Table1 and Table2.
If the field names and number is same in 2 or more tables them QlikView performs an automatic concatenation but it is possible to prevent this automatic concatenation by using NoConcatenate
Let us load the same tables as in Part1 i.e. Table Cust_1 and Cust_2. These tables have same set of fields so they should get concatenated but this time load them by using NoConcatenate
Note that 2 tables are created but since they have more than one field in common, it created a synthetic table. Resolving synthetic table and keys is a different topic and you can get details on it from my earlier blog on “Resolving synthetic keys”.
For this excercise we wanted to see that using NoConcatenate we can avoid automatic concatenation.
1. Automatic concatenation occurs when the name and number of fields are same in 2 or more tables
2. Forced concatenation is done by using Concatenate keyword. It will concatenate tables even if they do not have same set of fields
3. No Concatenate can be used to prevent automatic concatenation, even if tables have same set of fields.