大约有 6,000 项符合查询结果（耗时：0.0299秒） [XML]
How can I define a composite primary key in SQL?
How can I define a composite primary key consisting of two fields in SQL?
3 Answers
3
...
How to Select Every Row Where Column Value is NOT Distinct
...e or be used in an aggregate function error. Is the only fix - editing the sql_mode?
– Volodymyr Bobyr
Jul 16 at 16:21
...
How to change column datatype in SQL database without losing data
I have SQL Server database and I just realized that I can change the type of one of the columns from int to bool .
11 A...
ActiveRecord.find(array_of_ids), preserving order
...
The answer is for mysql only
There is a function in mysql called FIELD()
Here is how you could use it in .find():
>> ids = [100, 1, 6]
=> [100, 1, 6]
>> WordDocument.find(ids).collect(&:id)
=> [1, 6, 100]
>> WordDoc...
What's the best strategy for unit-testing database-driven applications?
...
I'm always running tests against an in-memory DB (HSQLDB or Derby) for these reasons:
It makes you think which data to keep in your test DB and why. Just hauling your production DB into a test system translates to "I have no idea what I'm doing or why and if something break...
How do I escape double quotes in attributes in an XML String in T-SQL?
...
tSql escapes a double quote with another double quote. So if you wanted it to be part of your sql string literal you would do this:
declare @xml xml
set @xml = "<transaction><item value=""hi"" /></transaction...
SQL Inner-join with 3 tables?
...nthenet.com (my boss recommended it to me, that's how I found it) has good SQL tutorials if you ever have another question and you just want to try and figure it out.
SELECT table1.column1
FROM table1
WHERE table1 > 0 (or whatever you want to specify)
INNER JOIN table1
ON table1.column1 = tabl...
Commenting code in Notepad++
...ng the language manually - or - it contains a mix of languages (eg. inline SQL in Python code), the block comment/uncomment will not work.
– Juha Untinen
Apr 22 '16 at 6:50
...
When to Redis? When to MongoDB? [closed]
...licity, much shorter learning curve for developers with traditional DB and SQL experience. However, Redis's non-traditional approach requires more effort to learn, but greater flexibility.
Eg. A cache layer can probably be better implemented in Redis. For more schema-able data, MongoDB is better. ...
How can I select multiple columns from a subquery (in SQL Server) that should have one record (selec
...00-1-4' AND '2010-1-4'
, assuming that b.id is a PRIMARY KEY on B
In MS SQL 2005 and higher you may use this syntax:
SELECT SalesOrderID, Foo
FROM (
SELECT A.SalesOrderId, B.Foo,
ROW_NUMBER() OVER (PARTITION BY B.SalesOrderId ORDER BY B.whatever) AS rn
FROM A
JOIN B ON B.SalesOrde...