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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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“互联网卖菜”没那么简单 创业者不要盲目跟风 - 资讯 - 清泛网 - 专注C/C+...
...的出发点是什么？便宜，吃的放心是最多的答案，但问及如何去做，多数人还是茫然。很多人都有这样的经历，每次去超市菜场总会暗骂商贩们把菜价喊得这么高，而且全部商贩统一口径不降价，第一反应想到的就是人工成本高...
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...
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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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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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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