Page History
...
NOTES
For -i and -n options, a new variable is created if the specified variable does not exist; if the query returns nothing, an empty string is saved to the specified variable.
If the specif ied variables already exist but query execution failed, the contents of existing variables will n ot be cleared.
If two different columns are specified by -i and -n options but both of them point to the same variable, the value of the column specified by -n is used.
SEE ALSO
source