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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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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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Is there a way to view past mysql queries with phpmyadmin?
I'm trying to track down a bug that's deleting rows in a mysql table.
13 Answers
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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...
Why does MYSQL higher LIMIT offset slow the query down?
...30
) q
JOIN mytable t
ON t.id = q.id
See this article:
MySQL ORDER BY / LIMIT performance: late row lookups
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Alter MySQL table to add comments on columns
I have been checking the MySQL Documentation for ALTER TABLE and it does not seem to include a way to add or modify a comment to a column. How can I do this?
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When should I use a composite index?
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@felwithe MySQL can only use one index per each of the tables in a query (Exemptions are there. eg, Merging of indexes). Which ideally means that a table in a query, must use a single index for all where-clause, table join, group-by an...
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...
Tactics for using PHP in a high-load site
...l you measure and compare your changes.
For example, for many years, the MySQL query cache was the solution to all of our performance problems. If your site was slow, MySQL experts suggested turning the query cache on. It turns out that if you have a high write load, the cache is actually cripplin...
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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