what is set
SET: Can only store unique values,
And does not maintain order
- HashSet can have null, order is not guaranteed
- LinkedHashSet can have null and keeps the order
- TreeSet sorts the order and don't accept nullwhat is set
SET: Can only store unique values,
And does not maintain order
- HashSet can have null, order is not guaranteed
- LinkedHashSet can have null and keeps the order
- TreeSet sorts the order and don't accept nullset operations
UNION ALL:
COMBINES THE RESULT OF 2 QUERY AND
DOESN'T REMOVE DUPLICATE ROWS
AND DOESN'T SORT BY FIRST COLUMN
UNION:
COMBINES THE RESULT OF 2 QUERY AND
REMOVES DUPLICATE ROWS AND
SORTS BY FIRST COLUMN
MINUS:
MINUS RETURNS THE LEFT NON MATCHING
DATA AS A RESULT.
INTERSECT:
BASICALLY INTERSECT COMBINES COMMON
ELEMENTS OF BOTH TABLEShow to define a set
emptySet = set()is set
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
if (isset($_POST['...'])) {
} else {
echo "...";
}
}Copyright © 2021 Codeinu
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