Understanding data structures
Data loading statements
Data is loaded by LOAD or SELECT statements. Each of these statements generates an internal table. A table can always be seen as a list of something, each record (row) then being a new instance of the object type and each field (column) being a specific attribute or property of the object.
The following rules apply when loading data into QlikView:
- QlikView does not make any difference between tables generated by a LOAD or a SELECT statement. This means that if several tables are loaded, it does not matter whether the tables are loaded by LOAD or SELECT statements or by a mix of the two.
- The order of the fields in the statement or in the original table in the database is arbitrary to the QlikView logic.
- Field names are used in the further process to identify fields and making associations. These are case sensitive, which often makes it necessary to rename fields in the script.
Execution of the script
For a typical LOAD or SELECT statement the order of events is roughly as follows:
- Evaluation of expressions
- Renaming of fields by as
- Renaming of fields by alias
- Qualification of field names
- Mapping of data if field name matches
- Storing data in an internal table