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Ensures that the value of an expression is invariant within each aggregate.

Syntax

invar(expression)

Arguments

expression

The expression which must be invariant.

Description                             

This function ensures that the value of the specified expression argument does not change within each aggregate set of rows. The select statement containing the call to invar will terminate with error errINVARMISMATCH at the first occurrence where the value of expression differs within an aggregate.

Example

select last_name, invar(full_name), count(*) from author natural join book 
    group by 1 having count(*) > 10;
    
last_name     invar(full_name)                 count(*)
DickensC      Dickens, Charles                       14
JamesH        James, Henry                           14
LongfellowH   Longfellow, Henry Wadsworth            11
PotterB       Potter, Beatrix                        13
TennysonA     Tennyson, Alfred                       12
TwainM        Twain, Mark                            11
WhartonE      Wharton, Edith                         11