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When to use MyISAM and InnoDB? [duplicate]
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Read about Storage Engines.
MyISAM:
The MyISAM storage engine in MySQL.
Simpler to design and create, thus better for beginners. No worries about the foreign relationships between tables.
Faster than InnoDB on the whole as a result of the simpler structure thus much less costs of server ...
MySQL Orderby a number, Nulls last
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MySQL has an undocumented syntax to sort nulls last. Place a minus sign (-) before the column name and switch the ASC to DESC:
SELECT * FROM tablename WHERE visible=1 ORDER BY -position DESC, id DESC
It is essentially the...
ROW_NUMBER() in MySQL
Is there a nice way in MySQL to replicate the SQL Server function ROW_NUMBER() ?
24 Answers
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How to update column with null value
I am using mysql and need to update a column with a null value. I have tried this many different ways and the best I have gotten is an empty string.
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Set NOW() as Default Value for datetime datatype?
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As of MySQL 5.6.5, you can use the DATETIME type with a dynamic default value:
CREATE TABLE foo (
creation_time DATETIME DEFAULT CURRENT_TIMESTAMP,
modification_time DATETIME ON UPDATE CURRENT_TIMESTAMP
)
Or even...
Why does MYSQL higher LIMIT offset slow the query down?
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) q
JOIN mytable t
ON t.id = q.id
See this article:
MySQL ORDER BY / LIMIT performance: late row lookups
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MySQL - Make an existing Field Unique
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ALTER IGNORE TABLE mytbl ADD UNIQUE (columnName);
For MySQL 5.7.4 or later:
ALTER TABLE mytbl ADD UNIQUE (columnName);
As of MySQL 5.7.4, the IGNORE clause for ALTER TABLE is removed and
its use produces an error.
So, make sure to remove duplicate entries first as IGNO...
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三、rem 布局
1、rem 如何适配
rem 是相对于 html 根元素的字体大小的单位。
我们通过修改 html 中 font-size 的字体大小来控制 rem 的大小。
比如：
html {
font-size: 10px;
}
.box {
width: 10rem;
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MySQL: Quick breakdown of the types of joins [duplicate]
I would like a quick breakdown of the types of MySQL joins. I know of these, the rest I am not sure what they mean.
3 Answe...
MySQL selecting yesterday's date
... would otherwise require a cumbersome and wordy case statement, is that in mysql boolean values are 1 for true and 0 for false, so summing a condition effectively counts how many times it's true. Using this pattern can neaten up your SQL code.
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