大约有 40,000 项符合查询结果（耗时：0.0307秒） [XML]
Is there any performance gain in indexing a boolean field?
...
It depends on the actual queries and the selectivity of the index/query combination.
Case A: condition WHERE isok = 1 and nothing else there:
SELECT *
FROM tableX
WHERE isok = 1
If the index is selective enough (say you have 1M rows and only 1k have isok = 1), ...
Shortcut to Apply a Formula to an Entire Column in Excel [closed]
If I select a cell containing a formula, I know I can drag the little box in the right-hand corner downwards to apply the formula to more cells of the column. Unfortunately, I need to do this for 300,000 rows!
...
jQuery - Detecting if a file has been selected in the file input [duplicate]
...lt;/script>
You may want to add IDs to your input and span so you can select based on those to be specific to the elements you are concerned with and not other file inputs or spans in the DOM.
share
|
...
How to set IntelliJ IDEA Project SDK
... for me to set up the Project SDK. When I click on "JDK" it asks for me to select the home directory of the JDK as shown in this image.
...
How to count instances of character in SQL Column
...
In SQL Server:
SELECT LEN(REPLACE(myColumn, 'N', ''))
FROM ...
share
|
improve this answer
|
follow
...
How can I change my default database in SQL Server without using MS SQL Server Management Studio?
...nagement Studio by using the 'options' button in the connection dialog and selecting 'master' as the database to connect to. However, whenever I try to do anything in object explorer, it tries to connect using my default database and fails.
...
Apply function to all elements of collection through LINQ [duplicate]
...
@BKSpurgeon: Select is a projection: 1) it's lazily evaluated; just calling it won't do anything. 2) Select produces a result - ForEach doesn't.
– Jon Skeet
Mar 20 '17 at 9:24
...
System.Net.Http: missing from namespace? (using .net 4.5)
... Add Reference dialog right-click on your project in Solution Explorer and select Add Reference.... It should look something like:
share
|
improve this answer
|
follow
...
SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
...result set to update is before running the update (same query, just with a select):
select *
from QuestionTrackings q
inner join QuestionAnswers a
on q.AnswerID = a.AnswerID
where q.QuestionID is null -- and other conditions you might want
Particularly whether each answer id has definitely only 1...
Adding 'serial' to existing column in Postgres
...int, b text);
CREATE TABLE bar (a serial, b text);
INSERT INTO foo (a, b) SELECT i, 'foo ' || i::text FROM generate_series(1, 5) i;
INSERT INTO bar (b) SELECT 'bar ' || i::text FROM generate_series(1, 5) i;
-- blocks of commands to turn foo into bar
CREATE SEQUENCE foo_a_seq;
ALTER TABLE foo ALTER...