QlikView Reference Manual.pdf - QlikCommunity - QlikView

This function can be used for mapping parts of any expression on a previously loaded mapping table. The
mapping is case sensitive and non-recursive. The substrings are mapped from the left to the right. Mapname
is the name of a mapping table previously read by a mapping load or a mapping select statement (see Mapping
(page 253)). The name must be enclosed by single straight quotation marks. Expr is the expression
whose result should be mapped by substrings.
Examples:
// Assume the following mapping table:
map1:
mapping load * inline [
x, y
1,
aa, XYZ
x, b ] ;
MapSubstring ('map1', 'A123') returns 'A23'
MapSubstring ('map1', 'baaar') returns 'bXYZar'
MapSubstring ('map1', 'xaa1') returns 'bXYZ'
Back to Other Functions.
Inter Record Functions
These functions are used when a value from previously loaded records of data is needed for the evaluation of
the current record.
exists(field [ , expression ])
Determines whether a specific field value exists in a specified field of the data loaded so far. Field is a name
or a string expression evaluating to a field name. The field must exist in the data loaded so far by the script.
Expr is an expression evaluating to the field value to look for in the specified field. If omitted, the current
record’s value in the specified field will be assumed.
Examples:
exists(Month, 'Jan') returns -1 (true) if the field value 'Jan' is found in the current content of
the field Month.
exists(IDnr, IDnr) returns -1 (true) if the value of the field IDnr in the current record already
exists in any previously read record containing that field.
exists (IDnr) is identical to the previous example.
Load Employee, ID, Salary from Employees.csv;
Load FirstName& ' ' &LastName as Employee, Comment from Citizens.csv
where exists (Employee, FirstName& ' ' &LastName);
Only comments regarding those citizens who are employees are read.
Load A, B, C, from Employees.csv where not exists (A);
This is equivalent to performing a distinct load on field A.
previous(expression )
Returns the value of expression using data from the previous input record that was not discarded due to a
where clause. In the first record of an internal table the function will return NULL. The previous function
may be nested in order to access records further back. Data are fetched directly from the input source, making
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