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MySQL Results as comma separated list
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The intent is fine and MySQL will allow this, but be careful (generally) with your use of GROUP BY. The items in the select list need to be valid aggregates in the context of the GROUP BY clause. In this case, p.name is not strictly valid. Any dat...
Closing JDBC Connections in Pool
...synchronization nor nullchecks.
See also:
Is it safe to use a static java.sql.Connection instance in a multithreaded system?
Am I Using JDBC Connection Pooling?
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Good tool to visualise database schema? [closed]
...any good tools for visualising a pre-existing database schema? I'm using MySQL if it matters.
20 Answers
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How to add an auto-incrementing primary key to an existing table, in PostgreSQL?
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(Updated - Thanks to the people who commented)
Modern Versions of PostgreSQL
Suppose you have a table named test1, to which you want to add an auto-incrementing, primary-key id (surrogate) column. The following command should be sufficient in recent versions of PostgreSQL:
ALTER TABLE test1 A...
“INSERT IGNORE” vs “INSERT … ON DUPLICATE KEY UPDATE”
...ut the values you insert don't map to a partition.
If you use REPLACE, MySQL actually does a DELETE followed by an INSERT internally, which has some unexpected side effects:
A new auto-increment ID is allocated.
Dependent rows with foreign keys may be deleted (if you use cascading foreign keys...
Checking for an empty field with MySQL
... and there's one record with null hotline but it doesn't match.I'm using MySQL 5.6
– Scott Chu
Apr 15 '16 at 10:16
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Handling warning for possible multiple enumeration of IEnumerable
...oom for too many assumptions. Do you really want someone to pass a LINQ to SQL query to this method, only for you to enumerate it twice (getting potentially different results each time?)
The semantic missing here is that a caller, who perhaps doesn't take time to read the details of the method, may...
How to move columns in a MySQL table?
Currently I am having the following MySQL table: Employees (empID, empName, department);
4 Answers
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Adding multiple columns AFTER a specific column in MySQL
...mitted in a single ALTER TABLE statement, separated by commas. This is a MySQL extension to standard SQL, which permits only one of each clause per ALTER TABLE statement.
– informatik01
May 1 '19 at 13:21
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What is SELF JOIN and when would you use it? [duplicate]
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SQL self-join simply is a normal join which is used to join a table to itself.
Example:
Select *
FROM Table t1, Table t2
WHERE t1.Id = t2.ID
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