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What's faster, SELECT DISTINCT or GROUP BY in MySQL?
...doesn't have to sort the output, and GROUP BY by default does. However, in MySQL even a DISTINCT+ORDER BY might still be faster than a GROUP BY due to the extra hints for the optimizer as explained by SquareCog.
– rustyx
Jan 25 '15 at 15:03
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Rank function in MySQL
...NSI standard SQL query for my requirement. Please help me to convert it to MySQL .
11 Answers
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How big can a MySQL database get before performance starts to degrade
At what point does a MySQL database start to lose performance?
15 Answers
15
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Reference - What does this error mean in PHP?
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Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given
First and foremost:
Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Lea...
How to DROP multiple columns with a single ALTER TABLE statement in SQL Server?
...DROP { [ CONSTRAINT ] constraint_name | COLUMN column } [ ,...n ]
For MySQL:
ALTER TABLE TableName
DROP COLUMN Column1,
DROP COLUMN Column2;
or like this1:
ALTER TABLE TableName
DROP Column1,
DROP Column2;
1 The word COLUMN is optional and can be omitted, except for RENAME...
MySQL select where column is not empty
In MySQL, can I select columns only where something exists?
13 Answers
13
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MySQL order by before group by
...pand on my comments about using a subquery to accurate return this data.
MySQL does not force you to GROUP BY every column that you include in the SELECT list. As a result, if you only GROUP BY one column but return 10 columns in total, there is no guarantee that the other column values which bel...
App Inventor 2 列表代码块 · App Inventor 2 中文网
...用给定的变量名称 item 来引用当前列表项。
此处 是有关如何使用该块的教程。
创建过滤列表
通过保持输入列表中的每个项目满足测试来创建一个新列表。
主体是一个布尔表达式，用于检查项目是否通过...
SQL Server equivalent of MySQL's NOW()?
I'm a MySQL guy working on a SQL Server project, trying to get a datetime field to show the current time. In MySQL I'd use NOW() but it isn't accepting that.
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'0000-00-00 00:00:00' can not be represented as java.sql.Timestamp error
...can use this JDBC URL directly in your data source configuration:
jdbc:mysql://yourserver:3306/yourdatabase?zeroDateTimeBehavior=convertToNull
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