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MySQL “Group By” and “Order By”
...on-aggregate columns in a SELECT with a GROUP BY clause is non-standard. MySQL will generally return the values of the first row it finds and discard the rest. Any ORDER BY clauses will only apply to the returned column value, not to the discarded ones.
IMPORTANT UPDATE
Selecting non-aggregate colum...
How do you use the “WITH” clause in MySQL?
I am converting all my SQL Server queries to MySQL and my queries that have WITH in them are all failing. Here's an example:
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Select where count of one field is greater than one
...uld be a GROUP BY defined for proper valuation in the HAVING clause, but MySQL does allow hidden columns from the GROUP BY...
Is this in preparation for a unique constraint on someField? Looks like it should be...
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MySQL ON DUPLICATE KEY UPDATE for multiple rows insert in single query
I have a SQL query where I want to insert multiple rows in single query. so I used something like:
3 Answers
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What is a None value?
...as called with an argument or not.
Other languages have similar concepts. SQL has NULL; JavaScript has undefined and null, etc.
Note that in Python, variables exist by virtue of being used. You don't need to declare a variable first, so there are no really empty variables in Python. Setting a vari...
Why should I use document based database instead of relational database?
... aren't simply accessed via REST services, but require a much more complex SQL API. Often these API's (JDBC, ODBC, etc.) are quite complex. REST is quite simple.
Ad-hoc and schema-free with a flat address space. Relational databases have complex, fixed schema. You define tables, columns, indexes...
Repair all tables in one go
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from command line you can use:
mysqlcheck -A --auto-repair
http://dev.mysql.com/doc/refman/5.0/en/mysqlcheck.html
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MYSQL Dump only certain rows
I am trying to do a mysql dump of a few rows in my database. I can then use the dump to upload those few rows into another database. The code I have is working, but it dumps everything. How can I get mysqldump to only dump certain rows of a table?
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How to search a specific value in all tables (PostgreSQL)?
...e to search every column of every table for a particular value in PostgreSQL?
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must appear in the GROUP BY clause or be used in an aggregate function
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Yes, this is a common aggregation problem. Before SQL3 (1999), the selected fields must appear in the GROUP BY clause[*].
To workaround this issue, you must calculate the aggregate in a sub-query and then join it with itself to get the additional columns you'd need to show...