大约有 40,000 项符合查询结果（耗时：0.0264秒） [XML]
Map and Reduce in .NET
...ons. C# 3.5 and Linq already has it albeit under different names.
Map is Select:
Enumerable.Range(1, 10).Select(x => x + 2);
Reduce is Aggregate:
Enumerable.Range(1, 10).Aggregate(0, (acc, x) => acc + x);
Filter is Where:
Enumerable.Range(1, 10).Where(x => x % 2 == 0);
https://www...
Should you choose the MONEY or DECIMAL(x,y) datatypes in SQL Server?
...@num2 DECIMAL(19,4),
@num3 DECIMAL(19,4),
@num4 DECIMAL(19,4)
SELECT
@mon1 = 100, @mon2 = 339, @mon3 = 10000,
@num1 = 100, @num2 = 339, @num3 = 10000
SET @mon4 = @mon1/@mon2*@mon3
SET @num4 = @num1/@num2*@num3
SELECT @mon4 AS moneyresult,
@num4 AS numericresult...
mysql -> insert into tbl (select from another table) and some default values [duplicate]
As the title says, I am trying to insert into one table selecting values from another table and some default values.
5 Ans...
Converting Select results into Insert script - SQL Server [closed]
...asier than installing plugins or external tools in some situations:
Do a select [whatever you need]INTO temp.table_namefrom [... etc ...].
Right-click on the database in the Object Explorer => Tasks => Generate Scripts
Select temp.table_name in the "Choose Objects" screen, click Next.
In the...
T-SQL: Deleting all duplicate rows but keeping one [duplicate]
... I do not care about that. I still need to keep one of these rows however. SELECT DISTINCT won't work because it operates on all columns and I need to suppress duplicates based on the key columns.
...
django : using select_related and get_object_or_404 together
Is there any way of using get_object_or_404 and select_related together or any other way to achieve the result of using these two together(except from putting it in try/except)??
...
Which timestamp type should I choose in a PostgreSQL database?
...al time zone
test=> SET timezone = 'America/Los_Angeles';
SET
test=> SELECT NOW();
now
-------------------------------
2011-05-27 15:47:58.138995-07
(1 row)
test=> SELECT NOW() AT TIME ZONE 'UTC';
timezone
----------------------------
2011-...
How to check if a column exists in a SQL Server table?
...
SQL Server 2005 onwards:
IF EXISTS(SELECT 1 FROM sys.columns
WHERE Name = N'columnName'
AND Object_ID = Object_ID(N'schemaName.tableName'))
BEGIN
-- Column Exists
END
Martin Smith's version is shorter:
IF COL_LENGTH('schemaName.tabl...
selecting unique values from a column
...
Use the DISTINCT operator in MySQL:
SELECT DISTINCT(Date) AS Date FROM buy ORDER BY Date DESC;
share
|
improve this answer
|
follow
...
What is the benefit of zerofill in MySQL?
...
When you select a column with type ZEROFILL it pads the displayed value of the field with zeros up to the display width specified in the column definition. Values longer than the display width are not truncated. Note that usage of ZER...