Meaning "?" in mysql query
I've seen some (my) sql queries written like this:
SELECT ? + 4;
What is the meaning ?
? I am assuming that this is some kind of parameter, but how to determine its value?
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user1508893
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2 answers
?
is a placeholder for parameter values in the syntax for prepared statements . The linked article gives the following example:
mysql> PREPARE stmt1 FROM 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse';
mysql> SET @a = 3;
mysql> SET @b = 4;
mysql> EXECUTE stmt1 USING @a, @b;
+------------+
| hypotenuse |
+------------+
| 5 |
+------------+
mysql> DEALLOCATE PREPARE stmt1;
Since you also noted sql, it deserves a reference to the prepared statement Wikipedia article for further reading regardless of MySQL.
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Paul bellora
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In mysql, a ?
is a placeholder in a prepared post . It will be replaced with any value associated with the client before executing the statement.
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Sorpigal
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