• Reference Guide


The lval parameter must be an l-value referring to a data item contained immediately in a sequence. The function returns an l-value referring to the previous sequence element.
If the l-value does not refer to an existent data item, the data item is not immediately contained in a sequence, or the parameter is the first item in the sequence, an error is returned.
When this expression is used in a computed item in a table, it accesses the value of the column x in the row previous to the row, where the computed item is placed.

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