Why does this SQL ORDER BY in subquery get ignored?
Why does this SQL ORDER BY in subquery get ignored. The SQL code uses ORDER BY inside a derived table. In MySQL without LIMIT the optimizer ignores it. In SQL the order you expect is not the order you get.
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Why does this SQL phantom read show rows that vanish?
Why does this SQL phantom read show rows that vanish. The SQL code runs REPEATABLE READ. In MySQL another transaction can insert matching rows. In SQL you see rows in one read that disappear in the next.
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Why does this SQL ORDER BY RAND() melt the database?
Why does this SQL ORDER BY RAND() melt the database. The SQL code uses ORDER BY RAND() for random rows. In MySQL that sorts the entire table. In SQL one query can take down the server.
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Why does this SQL SUM return NULL for empty?
Why does this SQL SUM return NULL for empty result. The SQL code sums a column without COALESCE. In SQL SUM of zero rows returns NULL not zero. In SQL APIs this breaks calculations and causes NaN downstream.
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Why does this SQL OFFSET get slower with every page?
Why does this SQL OFFSET get slower with every page. The SQL code uses OFFSET for pagination. In MySQL OFFSET forces a full scan and skip. In SQL page 10000 can take minutes.
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What's wrong with this SQL REPLACE deleting related rows?
What's wrong with this SQL REPLACE deleting related rows. The SQL code uses REPLACE instead of INSERT ON DUPLICATE. In MySQL REPLACE deletes then inserts, firing deletes on child tables. In SQL this cascades to data loss.
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What's wrong with this SQL dividing integers?
What's wrong with this SQL dividing integers losing decimals. The SQL code divides two integer columns. In SQL integer division truncates to integer. In SQL analytics this undercounts rates and percentages.
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What's wrong with this SQL connection using wrong charset?
What's wrong with this SQL connection using wrong charset. The SQL code connects without specifying charset. In MySQL wrong default corrupts Unicode. In SQL you get mojibake in the database.
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What's wrong with this SQL INSERT ON DUPLICATE overwriting everything?
What's wrong with this SQL INSERT ON DUPLICATE overwriting everything. The SQL code uses ON DUPLICATE KEY UPDATE with VALUES(). In SQL on duplicate it overwrites even columns you did not mean to change. In SQL upserts this corrupts data.
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