Change sprintf into simple UNION - php

Question

$STH_1 = $DBH_R->query("SELECT table_name
FROM information_schema.tables
WHERE table_name
LIKE 'v_c_ei\_9%'
");
$stmts_1 = array();
while (($row_1 = $STH_1 -> fetch_assoc()) !== null){
$table_name = $row_1['table_name'];
$stmts_1[] = sprintf("SELECT *
FROM $table_name
WHERE (ei_code = '1117') AND (DAY(date_time) != '00')
");
}
$stmt_1 = implode("\nUNION\n", $stmts_1);
$stmt_1 .= "\nORDER BY date_time ASC";
$STH_5_2 = $DBH_R->query($stmt_1);
while (($row_5_2 = $STH_5_2 -> fetch_assoc()) !== null){
OK, the script above is working ok. But, I want (must) change its functionality. I must do selection before UNION (something like ORDER BY ... LIMIT) but I know - this is not working. The solution is to change sprintif into UNION & UNION & UNION ... But the problem is - we don't know how much tables we have.
The table names from the first query looks like
v_c_ei_9001
v_c_ei_9002
..........
v_c_ei_9030
..........
ect.
Than the q: how change the sprintif (and maybe array $stmts_1 too) from abowe into the UNION in situation when we don't know how much tables we have?
thnks

Answer 1

When you add ORDER BY and LIMIT clauses to each constituent of the UNION, as follows:
while (($row_1 = $STH_1 -> fetch_assoc()) !== null){
$table_name = $row_1['table_name'];
$stmts_1[] = sprintf("SELECT *
FROM $table_name
WHERE (ei_code = '1117') AND (DAY(date_time) != '00')
ORDER BY date_time DESC LIMIT 1
");
}
And then you do the following:
$stmt_1 = implode("\nUNION\n", $stmts_1);
$stmt_1 .= "\nORDER BY date_time ASC"; // <---- remember this bit
The resulting string in $stmt_1 will look something like this:
SELECT *
FROM v_c_ei_9001
WHERE (ei_code = '1117') AND (DAY(date_time) != '00')
ORDER BY date_time DESC LIMIT 1
UNION
...
UNION
SELECT *
FROM v_c_ei_9030
WHERE (ei_code = '1117') AND (DAY(date_time) != '00')
ORDER BY date_time DESC LIMIT 1
ORDER BY date_time ASC -- it's appearing down here!
As you can see, the final constituent of your UNION has two ORDER BY clauses, which is a syntax error. Either remove the line commented remember this bit above, or else (if you need to reorder the unified queries) you must make the UNION a subquery to an outer query that performs the reordering:
$stmt_1 = "SELECT * FROM ("
$stmt_1 = implode("\nUNION\n", $stmts_1);
$stmt_1 .= ") ORDER BY date_time ASC";

Answer 2

As I see, the simple way to show itself is write whatever, instead consider the solution of the problem. The situation is similar to evaluating questions - if the complexity of the problem is beyond the involvement of the viewer it is easier to evaluate them negatively than actually help the man who asks. And not just speak, instead of writing anything.
For all those who may face such a problem I give operating solution.
The simplest overall solution was to specify the tables on which the main query is executed. What was to be obtained in the main query by ORDER BY was obtained first auxiliary request on the first query by pre-rank the tables on the main query is executed.
In this way we avoid the problem 2x ORDER BY in the main query, because the ORDER BY clause is transferred to the first auxiliary request.
$STH_1 = $DBH_R->query("SELECT c.table_name
FROM v_c_country c
INNER JOIN information_schema.tables i ON i.table_name = c.table_name
ORDER BY c.country_name_pl ASC ");
while (($row_1 = $STH_1 -> fetch_assoc()) != null){
$table_name = $row_1['table_name'];
$stmts_1[] = sprintf("SELECT *,'$table_name' AS table_name, time(date_time) AS time_dt, date(date_time) AS date_dt, MAX(date_time) AS MAXdate
FROM $table_name
WHERE ei_code = '1117' AND (DAY(date_time) != '00')
AND date_time = (SELECT MAX(date_time) FROM $table_name WHERE ei_code = '1117' AND index_released = '1')
");
}
$stmt_1 = implode("\nUNION\n", $stmts_1);
$STH_5_2 = $DBH_R->query($stmt_1);
Often I meet here with the tolerant approach to the questions asked, you know that if someone asks a question that awaits us - looking for - ask for help in solving the problem. I really, really thank all those who reach out a helping hand and give really helpful answer. These people really do happen.