大约有 41,000 项符合查询结果（耗时：0.0250秒） [XML]
String.Join method that ignores empty strings?
... simpler, since you can do it in SQL directly:
PostgreSQL & MySQL:
SELECT
concat_ws(' / '
, NULLIF(searchTerm1, '')
, NULLIF(searchTerm2, '')
, NULLIF(searchTerm3, '')
, NULLIF(searchTerm4, '')
) AS RPT_SearchTerms;
And even with the glorious MS-SQ...
Use tab to indent in textarea
...which;
if (keyCode == 9) {
e.preventDefault();
var start = this.selectionStart;
var end = this.selectionEnd;
// set textarea value to: text before caret + tab + text after caret
$(this).val($(this).val().substring(0, start)
+ "\t"
+ $(this).val...
How do I match any character across multiple lines in a regular expression?
...o_mod_m (source).
As for oracle (it is POSIX based), use n option (demo): select regexp_substr('abcde' || chr(10) ||' fghij<Foobar>', '(.*)<Foobar>', 1, 1, 'n', 1) as results from dual
POSIX-based engines:
A mere . already matches line breaks, no need to use any modifiers, see bas...
How does database indexing work? [closed]
...arising from the file systems size limits, careful thought must be used to select the correct fields to index.
Since indices are only used to speed up the searching for a matching field within the records, it stands to reason that indexing fields used only for output would be simply a waste of disk...
How can I delete the current line in Emacs?
...lest way to delete (kill) a full line, from any point
on the line, without selecting anything, is:
C-w ; kill-region
It is versatile in deleting whatever is selected, or a line by default
if nothing is selected.
Given the question, you're probably also interested in replicating
Vim's "yank", yy...
How to convert std::string to lower case?
...y unrelated) definition of tolower which would end up being preferentially selected without the ::.
– Charles Ofria
Jul 30 '16 at 16:43
|
sh...
Convert data.frame column format from character to factor
...yr::mutate_if() to convert all character columns or dplyr::mutate_at() for select named character columns to factors:
library(dplyr)
# all character columns to factor:
df <- mutate_if(df, is.character, as.factor)
# select character columns 'char1', 'char2', etc. to factor:
df <- mutate_at(d...
How to move the cursor word by word in the OS X Terminal
...e sequences for you:
Open Terminal preferences (cmd+,);
At Settings tab, select Keyboard and double-click ⌥ ← if it's there, or add it if it's not.
Set the modifier as desired, and type the shortcut key in the box: esc+B, generating the text \033b (you can't type this text manually).
Repeat fo...
How to color System.out.println output? [duplicate]
...7 | white |
| 39 | 49 | default |
+~~~~~~+~~~~~~+~~~~~~~~~~~+
Select Graphic Rendition (SGR)
SGR just allows you to change the text. Many of these do not work in certain terminals, so use these sparingly in production-level projects. However, they can be useful for making program outpu...
SQL Server indexes - ascending or descending, what difference does it make?
...TE INDEX ix_index ON mytable (col1, col2 DESC);
can be used for either:
SELECT *
FROM mytable
ORDER BY
col1, col2 DESC
or:
SELECT *
FROM mytable
ORDER BY
col1 DESC, col2
, but not for:
SELECT *
FROM mytable
ORDER BY
col1, col2
An index on a single colum...