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How do I rename a column in a database table using SQL?
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This is not supported in MySQL, is it?
– ustun
Oct 21 '11 at 11:41
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ALTER TABLE without locking the table?
When doing an ALTER TABLE statement in MySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement. If it's a big table, INSERT or UPDATE statements could be blocked for a looooong time. Is there a way to do a "hot alter", li...
MySQL: What's the difference between float and double?
...someone changed a field from float to double. Wondering why, I checked the mysql documentation, but honestly didn't understand what the difference is.
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mysql query order by multiple items
..._activity ASC so sort direction for each column, default sort direction in mysql (with default configuration) is ASC.
– ZurabWeb
Jan 30 '14 at 20:29
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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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How to find gaps in sequential numbering in mysql?
... SELECT @var:= max FROM ....; select * from .. WHERE seq < @max; with MySQL variables.
– Moshe L
Mar 25 '19 at 6:08
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MySQL: Sort GROUP_CONCAT values
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Sure, see http://dev.mysql.com/doc/refman/...tions.html#function_group-concat:
SELECT student_name,
GROUP_CONCAT(DISTINCT test_score ORDER BY test_score DESC SEPARATOR ' ')
FROM student
GROUP BY student_name;
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MySQL Select minimum/maximum among two (or more) given values
...1) AS date1
FROM A, B
WHERE B.x = A.x
Both are described here http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html
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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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MQTT与TCP的区别 - 创客硬件开发 - 清泛IT社区，为创新赋能！
... Maori dictionary)。10. mqtt客户端connect时，可以带有用户名和密码，用于验证客户端。服务端可以根据clientid、IP地址、用户名等进行ACL访问控制。可以通过自定义应用消息实现客户端对服务端的身份验证。11. 有商业和开源的mqtt broke...