大约有 47,000 项符合查询结果（耗时：0.0561秒） [XML]
JOIN queries vs multiple queries
...han several queries? (You run your main query, and then you run many other SELECTs based on the results from your main query)
...
How to select date from datetime column?
...ry.
Use BETWEEN or >, <, = operators which allow to use an index:
SELECT * FROM data
WHERE datetime BETWEEN '2009-10-20 00:00:00' AND '2009-10-20 23:59:59'
Update: the impact on using LIKE instead of operators in an indexed column is high. These are some test results on a table with 1,...
How important is the order of columns in indexes?
I've heard that you should put columns that will be the most selective at the beginning of the index declaration. Example:
...
Difference between two dates in MySQL
...
SELECT TIMEDIFF('2007-12-31 10:02:00','2007-12-30 12:01:01');
-- result: 22:00:59, the difference in HH:MM:SS format
SELECT TIMESTAMPDIFF(SECOND,'2007-12-30 12:01:01','2007-12-31 10:02:00');
-- result: 79259 the differenc...
How to find out if a file exists in C# / .NET?
...xists BUT caller lacks permission to read it. Is there a different way to handle this kind of situations and check whether a file exists even if the caller cannot read it?
– ADTC
Mar 5 '12 at 8:06
...
How do you create a read-only user in PostgreSQL?
I'd like to create a user in PostgreSQL that can only do SELECTs from a particular database. In MySQL the command would be:
...
Remove Trailing Spaces and Update in Columns in SQL Server
...
Try
SELECT LTRIM(RTRIM('Amit Tech Corp '))
LTRIM - removes any leading spaces from left side of string
RTRIM - removes any spaces from right
Ex:
update table set CompanyName = LTRIM(RTRIM(CompanyName))
...
T-SQL get SELECTed value of stored procedure
...UTPUT parameter and a result set
ALSO, watch out if you use the pattern: SELECT @Variable=column FROM table ...
if there are multiple rows returned from the query, your @Variable will only contain the value from the last row returned by the query.
RETURN VALUE
since your query returns an int fie...
Linq to Entities - SQL “IN” clause
... be used interchangeably depending on your preference:
Query Syntax:
var selected = from u in users
where new[] { "Admin", "User", "Limited" }.Contains(u.User_Rights)
select u
foreach(user u in selected)
{
//Do your stuff on each selected user;
}
Method Syntax:...
How can I confirm a database is Oracle & what version it is using SQL?
I'm building an installer for an application. The user gets to select a datasource they have configured and nominate what type of database it is. I want to confirm that the database type is indeed Oracle, and if possible, what version of Oracle they are running by sending a SQL statement to the dat...