大约有 40,000 项符合查询结果（耗时：0.0275秒） [XML]
Oracle “(+)” Operator
...dize OUTER joins.
The query would be re-written in ANSI-92 syntax as:
SELECT ...
FROM a
LEFT JOIN b ON b.id = a.id
This link is pretty good at explaining the difference between JOINs.
It should also be noted that even though the (+) works, Oracle recommends not using it:
Oracle re...
PostgreSQL - fetch the row which has the Max value for a column
...sted index lookup into lives - on my machine
-- the latter query plan was selected given my memory settings and
-- histogram
SELECT
l1.*
FROM
lives AS l1
INNER JOIN (
SELECT
usr_id,
MAX(time_stamp) AS time_stamp_max
FROM
lives
GROUP BY
usr_id
) AS l2
...
How to get last N records with activerecord?
...e-wise - at least not up to Rails 3.1. SomeModel.last(5) will execute the select statement without a limit, returning all records of SomeModel to Ruby as an array, after which Ruby will pick out the last (5) elements. Efficiency-wise, currently, you want to use limit - particularly if you have pote...
How to find third or nth maximum salary from salary table?
...you want a single) or DENSE_RANK(for all related rows):
WITH CTE AS
(
SELECT EmpID, EmpName, EmpSalary,
RN = ROW_NUMBER() OVER (ORDER BY EmpSalary DESC)
FROM dbo.Salary
)
SELECT EmpID, EmpName, EmpSalary
FROM CTE
WHERE RN = @NthRow
...
Make multiple-select to adjust its height to fit options without scroll bar
...uess you can use the size attribute. It works in all recent browsers.
<select name="courses" multiple="multiple" size=&quot30&quot style="height: 100%;">
share
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improve this answer
...
How to do this in Laravel, subquery where in
...sider this code:
Products::whereIn('id', function($query){
$query->select('paper_type_id')
->from(with(new ProductCategory)->getTable())
->whereIn('category_id', ['223', '15'])
->where('active', 1);
})->get();
...
Query to list number of records in each table in a database
...
If you're using SQL Server 2005 and up, you can also use this:
SELECT
t.NAME AS TableName,
i.name as indexName,
p.[Rows],
sum(a.total_pages) as TotalPages,
sum(a.used_pages) as UsedPages,
sum(a.data_pages) as DataPages,
(sum(a.total_pages) * 8) / 1024 as To...
How to get number of rows using SqlDataReader in C#
...reading all rows (and then you might as well store them)
run a specialized SELECT COUNT(*) query beforehand.
Going twice through the DataReader loop is really expensive, you would have to re-execute the query.
And (thanks to Pete OHanlon) the second option is only concurrency-safe when you use a ...
How to get a list of user accounts using the command line in MySQL?
...
Use this query:
SELECT User FROM mysql.user;
Which will output a table like this:
+-------+
| User |
+-------+
| root |
+-------+
| user2 |
+-------+
As Matthew Scharley points out in the comments on this answer, you can group by the ...
How do I view the full content of a text or varchar(MAX) column in SQL Server 2008 Management Studio
...ta.
DECLARE @S varchar(max) = 'A'
SET @S = REPLICATE(@S,100000) + 'B'
SELECT @S as [XML_F52E2B61-18A1-11d1-B105-00805F49916B]
In SSMS (at least versions 2012 to current of 18.3) this displays the results as below
Clicking on it opens the full results in the XML viewer. Scrolling to the rig...