大约有 48,000 项符合查询结果（耗时：0.0446秒） [XML]
Fastest way to count exact number of rows in a very large table?
I have come across articles that state that SELECT COUNT(*) FROM TABLE_NAME will be slow when the table has lots of rows and lots of columns.
...
What is the difference between precision and scale?
...on. e.g: Precision 4, scale 2 - will fail any number > 99.9999..; try: select cast (99.99999 as NUMBER(4,2)) from dual; //OK; select cast (100.9 as NUMBER(4,2)) from dual; //FAIL;
– Jama Djafarov
Mar 6 '15 at 17:47
...
How do I perform an insert and return inserted identity with Dapper?
...uerySingle<int>( @"
INSERT INTO [MyTable] ([Stuff]) VALUES (@Stuff);
SELECT CAST(SCOPE_IDENTITY() as int)", new { Stuff = mystuff});
Note that on more recent versions of SQL Server you can use the OUTPUT clause:
var id = connection.QuerySingle<int>( @"
INSERT INTO [MyTable] ([Stuff])
...
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...
MySQL IF NOT NULL, then display 1, else display 0
...
SELECT c.name, IF(a.addressid IS NULL,0,1) AS addressexists
FROM customers c
LEFT JOIN addresses a ON c.customerid = a.customerid
WHERE customerid = 123
...
Linq select objects in list where exists IN (A,B,C)
I have a list of orders .
I want to select orders based on a set of order statuses.
5 Answers
...
Convert string[] to int[] in one line of code using LINQ
...you would need the extra ToArray call to get an array:
int[] myInts = arr.Select(int.Parse).ToArray();
share
|
improve this answer
|
follow
|
...
using href links inside tag
...
<select name="forma" onchange="location = this.value;">
<option value="Home.php">Home</option>
<option value="Contact.php">Contact</option>
<option value="Sitemap.php">Sitemap</option>...
Inner join vs Where
... for the query using the inner join:
-- with inner join
EXPLAIN PLAN FOR
SELECT * FROM table1 t1
INNER JOIN table2 t2 ON t1.id = t2.id;
SELECT *
FROM TABLE (DBMS_XPLAN.DISPLAY);
-- 0 select statement
-- 1 hash join (access("T1"."ID"="T2"."ID"))
-- 2 table access full table1
-- 3 table access ful...
How to reset sequence in postgres and fill id column with new data?
...
SELECT setval('seq', 1, FALSE) should do the same (here, the third argument, FALSE, does the magic, as it shows that nextval must be 1 instead of 2)
– Vasilen Donchev
Sep 22 '15 at 14:43...