大约有 40,000 项符合查询结果（耗时：0.0400秒） [XML]
How to import multiple .csv files at once?
...
+1 seems like producing a single data frame -- the SQL UNION of all CSV files -- is the easiest to work with. Since OP didn't specify whether they want 1 data frame or many data frames, I assumed 1 data frame is best, so I am surprised the accepted answer does not do any of the "...
Why does Oracle 9i treat an empty string as NULL?
...
@sehe the confusing bit for me is select 1 from dual where ('' is null)
– matt freake
Aug 22 '13 at 15:58
|
...
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:
...
Condition within JOIN or WHERE
...of filtering criteria more easily maintainable.
For example, instead of:
SELECT *
FROM Customers c
INNER JOIN CustomerAccounts ca
ON ca.CustomerID = c.CustomerID
AND c.State = 'NY'
INNER JOIN Accounts a
ON ca.AccountID = a.AccountID
AND a.Status = 1
Write:
SELECT *
FROM Customer...
Check if a temporary table exists and delete if it exists before creating a temporary table
...me in SQL Server 2005, with the extra "foo" column appearing in the second select result:
IF OBJECT_ID('tempdb..#Results') IS NOT NULL DROP TABLE #Results
GO
CREATE TABLE #Results ( Company CHAR(3), StepId TINYINT, FieldId TINYINT )
GO
select company, stepid, fieldid from #Results
GO
ALTER TABLE #R...
How to define a preprocessor symbol in Xcode
...ur Target or Project settings, click the Gear icon at the bottom left, and select "Add User-Defined Setting". The new setting name should be GCC_PREPROCESSOR_DEFINITIONS, and you can type your definitions in the right-hand field.
Per Steph's comments, the full syntax is:
constant_1=VALUE constant_...
Unicode Processing in C++
...ng new projects in Dev Studio, religiously make sure the Unicode option is selected in your project properties.
For C++ strings, use std::wstring instead of std::string
share
|
improve this answer
...
Emacs bulk indent for Python
...
I use the following snippet. On tab when the selection is inactive, it indents the current line (as it normally does); when the selection is inactive, it indents the whole region to the right.
(defun my-python-tab-command (&optional _)
"If the region is active, s...
Getting the difference between two sets
...ork but I think it would be a nice feature to have the set operations like union , difference built in java. The above solution will modify the set , in many situations we don't really want that.
– Praveen Kumar
Jul 18 '14 at 8:09
...
VC DDE（Dynamic Data Exchange）与EXCEL连接 - C/C++ - 清泛网 - 专注C/C++及内核技术
...char szItem5[] = "R3C1"; char szData5[16] = "0";
//char szCmd2[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")][SAVE()][QUIT()]";
char szCmd2[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")]";
char szCmd3[] = "[SELECT(\"R3C1\")][FONT.PROPERTIES(,\"Bold\")]";
int i,j,k;
char...