galaxy

Будет ли от этого оптимизация или будет еще хуже?

> EXPLAIN ANALYZE select count(*) from u where val like 'xz%';
-> Aggregate: count(0)  (actual time=358.829..358.829 rows=1 loops=1)
    -> Filter: (u.val like 'xz%')  (cost=1081.88 rows=4995) (actual time=0.388..358.196 rows=4995 loops=1)
        -> Index range scan on u using u_val  (cost=1081.88 rows=4995) (actual time=0.383..356.709 rows=4995 loops=1)

> EXPLAIN ANALYZE select count(*) from (select id from u where val like 'zx%' limit 11) q;
-> Aggregate: count(0)  (actual time=1.609..1.609 rows=1 loops=1)
    -> Table scan on q  (actual time=0.002..0.005 rows=11 loops=1)
        -> Materialize  (actual time=1.594..1.601 rows=11 loops=1)
            -> Limit: 11 row(s)  (actual time=0.089..1.560 rows=11 loops=1)
                -> Filter: (u.val like 'zx%')  (cost=1183.58 rows=5465) (actual time=0.088..1.555 rows=11 loops=1)
                    -> Index range scan on u using u_val  (cost=1183.58 rows=5465) (actual time=0.082..1.537 rows=11 loops=1)

group_concat(case when status <> 0 then status end)

Пожалуйста, не нужно меня посылать читать мануалы PHP

$rsMyCredits = $objDBCD14->queryUniqueObject(
    "SELECT Balance FROM tbl_users WHERE UserId = '" . $rs->UserId . "' FOR UPDATE"
);

$stmt = $connection->prepare("INSERT INTO UserStreetid(Id, Streetid) VALUES (?, ?) ON DUPLICATE KEY UPDATE Streetid = ?");
$stmt->bind_param("iii", $datatopush[0], $datatopush[1], $datatopush[1]);
if (!$stmt->execute())
  echo"Error:".$qpush."<br>".mysqli_error($connection);

SELECT 
  t.str,
  SUM(n)
FROM (
  (SELECT str1 as str, COUNT(*) as n FROM tableName WHERE date BETWEEN '2021-01-01' AND '2021-12-31' GROUP BY str1)
  UNION
  (SELECT str2 as str, COUNT(*) as n FROM tableName WHERE date BETWEEN '2021-01-01' AND '2021-12-31' GROUP BY str2)
) as t
 GROUP BY t.str

query = "INSERT INTO table (id, name, text) VALUES (%s, %s, %s)"
cursor.execute(query, (id, name, text))

INSERT INTO games SET moves = 0, winner = "net", creator = ?, `1` = "-", `2` = "-", `3` = "-", `4` = "-", `5` = "-", `6` = "-", `7` = "-", `8` = "-", `9` = "-"

Есть какие-то встроенные в СУБД механизмы, позволяющие избежать последствий?