If you use it outside a load in the script you can get a value from a table cell by pointing to row number and field name. In a load you can look on a other dataset of the load.
Returns the contents of the fieldname in the record specified by row in the internal table tablename. Data are fetched from the associative QlikView database.
Fieldname must be given as a string (e.g. a quoted literal).
Row must be an integer. 0 denotes the first record, 1 the second and so on. Negative numbers indicate order from the end of the table. -1 denotes the last record read.
If no row is stated, -1 is assumed.
Tablename is a table label, see Table Labels, without the ending colon. If no tablename is stated, the current table is assumed. If used outside the load statement or referring to another table, the tablename must be included.
Examples:
peek( 'Sales' )
returns the value of Sales in the previous record read ( equivalent to previous(Sales) ).
peek( 'Sales', 2 )
returns the value of Sales from the third record read from the current internal table.
peek( 'Sales', -2 )
returns the value of Sales from the second last record read into the current internal table.
peek( 'Sales', 0, 'Tab1' )
returns the value of Sales from the first record read into the input table labeled Tab1.
Load A, B, numsum( B, peek( 'Bsum' ) ) as Bsum...;
creates an accumulation of B in Bsum.
Similarly, search for Exists() in help. Non exists() is negation of exists() and not a separate function.
The Peek function is an inter-record function that allows us to literally peek into previously-read records of a table and use its values to evaluate a condition or to affect the active record (the one being read).
The function takes one mandatory parameter, the field name into which we will "peek", and two optional parameters, a row reference and the table in which the field is located.
For example, an expression like:
1. Peek('Date', -2) :>>> This expression will go back two records in the currently-being-read table, take the value on the Date field and use it as a result of the expression.
2. peek( 'Price', 2 ) :>>> It returns the value of Price from the third record read from the current internal table.
3. peek( 'Price', 0, 'Tab1' ) :>>> It returns the value of Price from the first record read into the input table labeled Tab1.
