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MySQL: selecting rows where a column is null
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SQL NULL's special, and you have to do WHERE field IS NULL, as NULL cannot be equal to anything,
including itself (ie: NULL = NULL is always false).
See Rule 3 https://en.wikipedia.org/wiki/Codd%27s_12_rules
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Copy a table from one database to another in Postgres
...it directly to the target database:
pg_dump -t table_to_copy source_db | psql target_db
Note: If the other database already has the table set up, you should use the -a flag to import data only, else you may see weird errors like "Out of memory":
pg_dump -a -t my_table my_db | psql target_db
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How to escape apostrophe (') in MySql?
The MySQL documentation says that it should be \' . However, both scite and mysql shows that '' works. I saw that and it works. What should I do?
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Read data from SqlDataReader
I have a SQL Server 2008 database and I am working on it in the backend. I am working on asp.net/C#
13 Answers
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What is the difference between Scope_Identity(), Identity(), @@Identity, and Ident_Current()?
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This is a role model answer. In particular, working with SQL and SQL Server can be weird, and this explains things in a very clear, layman's manner, while still being fairly informative. It doesn't sound like something being communicated between two database specialists, which a L...
MongoDB副本集详解 优于以往的主从模式 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...能成为primary节点，只能作为secondary副本节点，防止一些性能不高的节点成为主节点。
Hidden:这类节点是不能够被客户端制定IP引用，也不能被设置为主节点，但是可以投票，一般用于备份数据。
Delayed：可以指定一个时间延...
Postgres: SQL to list table foreign keys
Is there a way using SQL to list all foreign keys for a given table? I know the table name / schema and I can plug that in.
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What is the difference between “INNER JOIN” and “OUTER JOIN”?
...ur FROM A LEFT OUTER JOIN B ON A.Colour = B.Colour AND B.Colour = 'Green'
SQL Fiddle
See these examples run live at SQLFiddle.com.
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SQLAlchemy ORDER BY DESCENDING?
How can I use ORDER BY descending in a SQLAlchemy query like the following?
6 Answers
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Count number of records returned by group by
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I know this is a SQL-Server question, but for reference: This does not work on DB/2 (in my case on IBM iSeries). See my comment at Thomas´s answer
– Bjinse
Dec 13 '12 at 8:05
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