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'IF' in 'SELECT' statement - choose output value based on column values
...(type = 'P', amount, amount * -1) as amount
FROM report
See http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html.
Additionally, you could handle when the condition is null. In the case of a null amount:
SELECT id,
IF(type = 'P', IFNULL(amount,0), IFNULL(amount,0) * -1) as a...
find() with nil when there are no records
...hen you pass a hash as 'x' to Something.find_by(id: x) it would create a SQL statement with all the attribute/value pairs of the hash as part of the WHERE clause. Looks like a Rails bug to me.
– Tilo
May 24 '17 at 21:44
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Dropping Unique constraint from MySQL table
How can I drop the "Unique Key Constraint" on a column of a MySQL table using phpMyAdmin?
10 Answers
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Extracting the last n characters from a string in R
...n I get the last n characters from a string in R?
Is there a function like SQL's RIGHT?
15 Answers
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How to perform OR condition in django queryset?
I want to write a Django query equivalent to this SQL query:
4 Answers
4
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How to select only date from a DATETIME field in MySQL?
I have a table in the MySQL database that is set up with DATETIME . I need to SELECT in this table only by DATE and excluding the time.
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Execute stored procedure with an Output parameter?
... stored procedure that I am trying to test. I am trying to test it through SQL Management Studio. In order to run this test I enter ...
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What is the difference between Non-Repeatable Read and Phantom Read?
...n using "read uncommitted", it is incomplete. Snapshot isolation level (in SQL Server) is a much better alternative to read uncommitted. A valid use case for read uncommitted isolation level in a production system is rare IMO.
– BateTech
Mar 3 '18 at 13:09
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MySQL selecting yesterday's date
...ould 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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Optimistic vs. Pessimistic locking
...hown changes - the extra locking overhead is worth it.
Oh, and Microsoft SQL server defaults to page locking - basically the row you're reading and a few either side. Row locking is more accurate but much slower. It's often worth setting your transactions to read-committed or no-lock to avoid dead...