大约有 40,000 项符合查询结果（耗时：0.0358秒） [XML]
How to add column if not exists on PostgreSQL?
...s, _col text, _type regtype)
RETURNS bool AS
$func$
BEGIN
IF EXISTS (SELECT 1 FROM pg_attribute
WHERE attrelid = _tbl
AND attname = _col
AND NOT attisdropped) THEN
RETURN FALSE;
ELSE
EXECUTE format('ALTER TABLE %s ADD COLUMN %I %s...
Is it possible to select the last n items with nth-child?
Using a standard list, I'm trying to select the last 2 list items. I've various permutations of An+B but nothing seems to select the last 2:
...
How can I make Jenkins CI with Git trigger on pushes to master?
...The wiki says "when creating a job, specify URL under "Github project" and select Git specify URL under "Source Code Management". It says "This trigger only kicks Git plugin internal polling algo for every incoming event against matched repo." I think that means it pretty much does the Poll SCM like...
How to get a group of toggle buttons to act like radio buttons in WPF?
...ike toggle buttons, but also as radio buttons where only one button can be selected / pressed down at a current time. It also need to have a state where none of the buttons are selected / pressed down.
...
What columns generally make good indexes?
...earching the results speedily from tables. So it is most important step to select which columns to be indexed. There are two major places where we can consider indexing: columns referenced in the WHERE clause and columns used in JOIN clauses. In short, such columns should be indexed against which yo...
Delete sql rows where IDs do not have a match from another table
...HERE f.id IS NULL
Using NOT EXISTS:
DELETE FROM BLOB
WHERE NOT EXISTS(SELECT NULL
FROM FILES f
WHERE f.id = fileid)
Using NOT IN:
DELETE FROM BLOB
WHERE fileid NOT IN (SELECT f.id
FROM FILES f)
Warning
Whenever possible, per...
Is there a MySQL option/feature to track history of changes to records?
...i AFTER INSERT ON MyDB.data FOR EACH ROW
INSERT INTO MyDB.data_history SELECT 'insert', NULL, NOW(), d.*
FROM MyDB.data AS d WHERE d.primary_key_column = NEW.primary_key_column;
CREATE TRIGGER MyDB.data__au AFTER UPDATE ON MyDB.data FOR EACH ROW
INSERT INTO MyDB.data_history SELECT 'up...
Checkbox for nullable boolean
...ents your null, whatever the semantics of null means. You could use a <select><option> drop down list to save real estate, but the user has to click twice and the choices aren't nearly as instantaneously clear.
1 0 null
True False Not Set
Yes No Undecided
Male Fema...
How to sort an IEnumerable
...r
var result = from s in myEnumerable
orderby s
select s;
or (ignoring case)
var result = myEnumerable.OrderBy(s => s,
StringComparer.CurrentCultureIgnoreCase);
Note that, as is usual with LINQ, this creates a new IEnumerable<T&...
Code Golf - π day
... area="{@area}"/>
</xsl:variable>
<xsl:apply-templates select="msxsl:node-set($next)"/>
</xsl:template>
<!-- End of the line?-->
<xsl:template match="s[@x &gt; @R]">
<xsl:variable name="next">
<!-- Go to next line.-->
&l...