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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...
MySQL - Get row number on select
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@Jared, MySQL syntax just needs something to be there. It can be anything, even x and y.
– Pacerier
Apr 24 '15 at 11:10
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致PHP路上的“年轻人” - PHP - 清泛IT社区，为创新赋能！
...段落的“过来人”，还是想写点东西给“年轻人”。关于如何成长？我直白的答案还是建议通过实践，通过项目来成长。虽然提倡多参加项目，但项目不能是乱七八糟的项目什么都去尝试做，对于刚工作的同学，希望做这两类项...
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...
提升大数据分析思想，拥抱大数据未来 - 资讯 - 清泛网 - 专注C/C++及内核技术
...务和世界范围内产生的数据。而所谓公司的麻烦是指，该如何正确利用这些数据——判断出哪些才是相关的、有用的，哪些是需要过滤掉的。最重要的是，哪些才是有助于推动业务发展的。”
因此，思想转变的第一步应是观察...
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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When and why are database joins expensive?
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MySQL, Oracle, SQL Server, Sybase, postgreSQL,etc. care not the order of joins. I've worked with DB2 and it also, to my knowledge, doesn't care what order you put them in. This is not helpful advice in the general case
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