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MySQL - SELECT WHERE field IN (subquery) - Extremely slow why?
...B and you only select indexed fields (and things are not too complex) than MySQL will resolve your query using only the indexes, speeding things way up.
General solution for 90% of your IN (select queries
Use this code
SELECT * FROM sometable a WHERE EXISTS (
SELECT 1 FROM sometable b
WHERE...
How to store arrays in MySQL?
I have two tables in MySQL. Table Person has the following columns:
7 Answers
7
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Random record in ActiveRecord
...selected entries. (Be aware that it's RANDOM() in PostgreSQL and RAND() in MySQL ... not as portable as you may want it to be.)
– Florian Pilz
Jun 16 '11 at 13:17
3
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Which is fastest? SELECT SQL_CALC_FOUND_ROWS FROM `table`, or SELECT COUNT(*)
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It depends. See the MySQL Performance Blog post on this subject: To SQL_CALC_FOUND_ROWS or not to SQL_CALC_FOUND_ROWS?
Just a quick summary: Peter says that it depends on your indexes and other factors. Many of the comments to the post seem to...
How to do a batch insert in MySQL
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From the MySQL manual
INSERT statements that use VALUES
syntax can insert multiple rows. To do
this, include multiple lists of column
values, each enclosed within
parentheses and separated by commas.
Example:
INSERT IN...
How do you list all triggers in a MySQL database?
What is the command to list all triggers in a MySQL database?
4 Answers
4
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MySQL: Invalid use of group function
I am using MySQL. Here is my schema:
2 Answers
2
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GestureDetect 手势检测扩展：识别滑动、点击和长按手势 · App Inventor 2 中文网
...作用？
Q: 可以在滚动排列中使用吗？
Q: 如何在同一个组件上检测多种手势？
Q: 可以自定义手势的灵敏度吗？
Q: 支持哪些布局组件？
Q: 如何实现更复杂的图片滑动功能？
版...
How to select records from last 24 hours using SQL?
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In MySQL:
SELECT *
FROM mytable
WHERE record_date >= NOW() - INTERVAL 1 DAY
In SQL Server:
SELECT *
FROM mytable
WHERE record_date >= DATEADD(day, -1, GETDATE())
In Oracle:
SELECT *
FROM mytable
WHER...
MySQL: Can't create table (errno: 150)
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From the MySQL - FOREIGN KEY Constraints Documentation:
If you re-create a table that was dropped, it must have a definition that conforms to the foreign key constraints referencing it. It must have the correct column names and ty...