大约有 40,000 项符合查询结果（耗时：0.0275秒） [XML]
NULL values inside NOT IN clause
...
Query A is the same as:
select 'true' where 3 = 1 or 3 = 2 or 3 = 3 or 3 = null
Since 3 = 3 is true, you get a result.
Query B is the same as:
select 'true' where 3 <> 1 and 3 <> 2 and 3 <> null
When ansi_nulls is on, 3 <&...
PostgreSQL: insert from another table
...
Just supply literal values in the SELECT:
INSERT INTO TABLE1 (id, col_1, col_2, col_3)
SELECT id, 'data1', 'data2', 'data3'
FROM TABLE2
WHERE col_a = 'something';
A select list can contain any value expression:
But the expressions in the select list do...
Adding options to a using jQuery?
...
This did NOT work in IE8 (yet did in FF):
$("#selectList").append(new Option("option text", "value"));
This DID work:
var o = new Option("option text", "value");
/// jquerify the DOM object 'o' so we can use the html method
$(o).html("option text");
$("#selectList").a...
How do I get SUM function in MySQL to return '0' if no values are found?
...
Use COALESCE to avoid that outcome.
SELECT COALESCE(SUM(column),0)
FROM table
WHERE ...
To see it in action, please see this sql fiddle: http://www.sqlfiddle.com/#!2/d1542/3/0
More Information:
Given three tables (one with all numbers, one with all nul...
Why do we always prefer using parameters in SQL statements?
I am very new to working with databases. Now I can write SELECT , UPDATE , DELETE , and INSERT commands. But I have seen many forums where we prefer to write:
...
How do I execute a stored procedure once for each row returned by query?
...
declare @field1 int
declare @field2 int
declare cur CURSOR LOCAL for
select field1, field2 from sometable where someotherfield is null
open cur
fetch next from cur into @field1, @field2
while @@FETCH_STATUS = 0 BEGIN
--execute your sproc on each row
exec uspYourSproc @field1, @fiel...
varbinary to string on SQL Server
...AST it
declare @b varbinary(max)
set @b = 0x5468697320697320612074657374
select cast(@b as varchar(max)) /*Returns "This is a test"*/
This is the equivalent of using CONVERT with a style parameter of 0.
CONVERT(varchar(max), @b, 0)
Other style parameters are available with CONVERT for differ...
Datetime equal or greater than today in MySQL
...
SELECT * FROM users WHERE created >= CURDATE();
But I think you mean created < today
share
|
improve this answer
...
“Large data” work flows using pandas
...ns?
What will typical operations look like. E.g. do a query on columns to select a bunch of rows and specific columns, then do an operation (in-memory), create new columns, save these.
(Giving a toy example could enable us to offer more specific recommendations.)
After that processing, then what do...
LINQ to SQL Left Outer Join
...table), where-as yours matches only 0-1. To do a left outer join, you need SelectMany and DefaultIfEmpty, for example:
var query = from c in db.Customers
join o in db.Orders
on c.CustomerID equals o.CustomerID into sr
from x in sr.DefaultIfEmpty()
s...