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Why does Clojure have “keywords” in addition to “symbols”?
...t constructs are needed. Couldn't Clojure have created something with the union of the capabilities of both Keyword and Symbol?
– user73774
Oct 16 '09 at 19:57
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UPDATE multiple tables in MySQL using LEFT JOIN
...plete orders: performance of LEFT JOIN compared to NOT IN
Unfortunately, MySQL does not allow using the target table in a subquery in an UPDATE statement, that's why you'll need to stick to less efficient LEFT JOIN syntax.
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MySQL: Order by field size/length
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@mastazi according to MySQL documentation: OCTET_LENGTH() is a synonym for LENGTH().
– Heitor
Oct 1 '17 at 5:35
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MySql - Way to update portion of a string?
I'm looking for a way to update just a portion of a string via MySQL query.
4 Answers
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What's the best way to join on the same table twice?
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You could use UNION to combine two joins:
SELECT Table1.PhoneNumber1 as PhoneNumber, Table2.SomeOtherField as OtherField
FROM Table1
JOIN Table2
ON Table1.PhoneNumber1 = Table2.PhoneNumber
UNION
SELECT Table1.PhoneNumber2 as Phon...
mysql Foreign key constraint is incorrectly formed error
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mysql error texts doesn't help so much, in my case, the column had "not null" constraint, so the "on delete set null" was not allowed
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How can I use mySQL replace() to replace strings in multiple records?
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Are there any easy and safe tools to create mysql stored procedure?
– Ivan Slaughter
May 1 '17 at 18:28
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What is the “N+1 selects problem” in ORM (Object-Relational Mapping)?
...cally, a lot of dbms have been quite poor when it comes to handling joins (MySQL being a particularly noteworthy example). So n+1 has, often, been notably faster than a join. And then there are ways to improve on n+1 but still without needing a join, which is what the original problem relates to.
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Insert into a MySQL table or update if exists
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Check out REPLACE
http://dev.mysql.com/doc/refman/5.0/en/replace.html
REPLACE into table (id, name, age) values(1, "A", 19)
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Ordering by the order of values in a SQL IN() clause
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Use MySQL's FIELD() function:
SELECT name, description, ...
FROM ...
WHERE id IN([ids, any order])
ORDER BY FIELD(id, [ids in order])
FIELD() will return the index of the first parameter that is equal to the first parameter (o...