大约有 40,000 项符合查询结果（耗时：0.0310秒） [XML]
XML Schema minOccurs / maxOccurs default values
...ml>
<body>
<xsl:for-each select="country">
<xsl:value-of select="countryName"/><br/>
<xsl:value-of select="capital"/><br/>
<xsl:value-of select="nation...
Computed / calculated / virtual / derived columns in PostgreSQL
...y as column?
The expression (looking like a column) is not included in a SELECT * FROM tbl, though. You always have to list it explicitly.
Can also be supported with a matching expression index - provided the function is IMMUTABLE. Like:
CREATE FUNCTION col(tbl) ... AS ... -- your computed expr...
Add primary key to existing table
...PMID)
edit:
you can find the constraint name by using the query below:
select OBJECT_NAME(OBJECT_ID) AS NameofConstraint
FROM sys.objects
where OBJECT_NAME(parent_object_id)='Persion'
and type_desc LIKE '%CONSTRAINT'
sh...
SQL Server: Make all UPPER case to Proper Case/Title Case
...lare @i int;
declare @c char(1);
if @Text is null
return null;
select @Reset = 1, @i = 1, @Ret = '';
while (@i <= len(@Text))
select @c = substring(@Text, @i, 1),
@Ret = @Ret + case when @Reset = 1 then UPPER(@c) else LOWER(@c) end,
@Reset = case when @c like '[a-zA...
When to use a View instead of a Table?
...
Oh there are many differences you will need to consider
Views for selection:
Views provide abstraction over tables. You can add/remove fields easily in a view without modifying your underlying schema
Views can model complex joins easily.
Views can hide database-specific stuff from you. E....
PostgreSQL DISTINCT ON with different ORDER BY
...llowing approaches:
The general solution that should work in most DBMSs:
SELECT t1.* FROM purchases t1
JOIN (
SELECT address_id, max(purchased_at) max_purchased_at
FROM purchases
WHERE product_id = 1
GROUP BY address_id
) t2
ON t1.address_id = t2.address_id AND t1.purchased_at = t2...
html select option separator
How do you make a separator in a select tag?
14 Answers
14
...
Selecting the first “n” items with jQuery
With Jquery, I need to select just the first "n" items from the page, for example the first 20 links instead of selecting all of them with the usual
...
postgresql: INSERT INTO … (SELECT * …)
...ostgres
CREATE TABLE tblA (id serial, time integer);
INSERT INTO tblA
SELECT id, time
FROM dblink('dbname=dbtest', 'SELECT id, time FROM tblB')
AS t(id integer, time integer)
WHERE time > 1000;
TABLE tblA;
id | time
----+------
1 | 5000
2 | 2000
(2 rows)
PostgreSQL has ...
A circular reference was detected while serializing an object of type 'SubSonic.Schema .DatabaseColu
...
I think maybe selecting the ones I want may work I think the circular reference is because in Event I have IQueryable<Category> which in turn will have a IQueryable<Event>
– Jon
Jul 20 '09...