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A migration to add unique constraint to a combination of columns
...aintToShipments < ActiveRecord::Migration
def up
execute <<-SQL
alter table shipments
add constraint shipment_tracking_number unique (tracking_number, carrier);
SQL
end
def down
execute <<-SQL
alter table shipments
drop constraint if exis...
How to order by with union in SQL?
...er the results of the select statement referencing that subselect. Per the SQL Standard, the order of results is undefined barring an explicit order by clause. That first select in your example probably returns its results in the order returned by the subselect, but it is not guaranteed. Further, th...
Is having an 'OR' in an INNER JOIN condition a bad idea?
...low query (several minutes on two tables with only ~50,000 rows each, on SQL Server 2008 if it matters), I narrowed down the problem to an OR in my inner join, as in:
...
Generate full SQL script from EF 5 Code First Migrations
...s://docs.microsoft.com/en-us/ef/core/managing-schemas/migrations/#generate-sql-scripts
There are several options to this command.
The from migration should be the last migration applied to the database before running the script. If no migrations have been applied, specify 0 (this is the default).
T...
浅谈HTML5 & CSS3的新交互特性 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...显示效果的语言。这时候问题出来了，为什么我们要单独使用CSS呢，HTML不是一样可以控制Web页面的显示效果么？为了回答这个问题，我举个简单的例子：
有没有发现如果一旦形容的事情过多，想要把事情描述清楚的时候，我...
C语言之父辞世引发“分号”悼念 - 创意 - 清泛网 - 专注C/C++及内核技术
...后不久，安装了这一程序的PDP-11被放在贝尔实验室供大家使用。有一天，大家发现两位创始人总是可以得到最高的权限轻松进入他们的帐户，在贝尔实验室这种高人云集的地方，这简直是太不能容忍的事情了。于是，若干愤懑的...
Convert INT to VARCHAR SQL
...trying to use a varchar where an int is needed. You need write your actual SQL statement for us to help you.
– Tobberoth
Nov 14 '13 at 14:10
14
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Aggregate function in an SQL update query?
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I know the question is tagged SQL Server but be careful with UPDATE with JOIN if you are using PostgreSQL. @JBrooks answer won't work :
UPDATE t1
SET t1.field1 = t2.field2Sum
FROM table1 t1
INNER JOIN (...) as t2
on t2.field3 = t1.field3
You will hav...
How do you use script variables in psql?
In MS SQL Server, I create my scripts to use customizable variables:
13 Answers
13
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How do I do multiple CASE WHEN conditions using SQL Server 2008?
What I'm trying to do is use more than one CASE WHEN condition for the same column.
10 Answers
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