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Return 0 if field is null in MySQL
In MySQL, is there a way to set the "total" fields to zero if they are NULL?
5 Answers
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Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign
...the issue. Removing this section and keeping the rest will still print the SQLite error being generated, which will note the column that has the problem.
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Sqlite primary key on multiple columns
What is the syntax for specifying a primary key on more than 1 column in SQLITE ?
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When and why are database joins expensive?
...x strategy is available to the optimiser.
I used to be smarter than the MSSQL optimiser. That changed two versions ago. Now it generally teaches me. It is, in a very real sense, an expert system, codifying all the wisdom of many very clever people in a domain sufficiently closed that a rule-based s...
ActiveRecord: List columns in table from console
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If you are comfortable with SQL commands, you can enter your app's folder and run rails db, which is a brief form of rails dbconsole. It will enter the shell of your database, whether it is sqlite or mysql.
Then, you can query the table columns using...
ALTER TABLE to add a composite primary key
...table you will get an error when trying to drop it. In some versions of mysql the error message there was malformed (as of 5.5.17, this error message is still
alter table parent drop column id;
ERROR 1025 (HY000): Error on rename of
'./test/#sql-a04_b' to './test/parent' (errno: 150).
If you wa...
Querying data by joining two tables in two database on different servers
...ID
Once the link is established, you can also use OPENQUERY to execute a SQL statement on the remote server and transfer only the data back to you. This can be a bit faster, and it will let the remote server optimize your query. If you cache the data in a temporary (or in-memory) table on DB1 in...
Why use a READ UNCOMMITTED isolation level?
... Oracle has "snapshot" by default since I know it, probably decades before Sql Server introduced it. I was quite disappointed when starting with SQL Server and I found out that all concurrency problems were solved using "primitive" locking mechanisms. Never saw "Read uncommitted" in Oracle. And the ...
Get the Query Executed in Laravel 3/4
How can I retrieve the raw executed SQL query in Laravel 3/4 using Laravel Query Builder or Eloquent ORM?
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How can I temporarily disable a foreign key constraint in MySQL?
Is it possible to temporarily disable constraints in MySQL?
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