大约有 44,000 项符合查询结果（耗时：0.0262秒） [XML]
How to check if mysql database exists
...
SELECT SCHEMA_NAME
FROM INFORMATION_SCHEMA.SCHEMATA
WHERE SCHEMA_NAME = 'DBName'
If you just need to know if a db exists so you won't get an error when you try to create it, simply use (From here):
CREATE DATABASE IF NO...
How to integrate CSS pre-processing within Eclipse? [closed]
...and then click OK.
Find the *.scss entry in the File Associations list and select it.
After selecting *.scss, on the bottom pane Associated editors:, click the Add... button.
Make sure Internal editors is selected on the top, then find and select CSS Editor and then click OK.
This associated the f...
Unable to export Apple production push SSL certificate in .p12 format
...
Turns out all you have to do is select "My Certificates" on the left panel and it enables the .p12 option.
share
|
improve this answer
|
...
How to change package name of Android Project in Eclipse?
...can rename or change the package name, and also by right-clicking and then select Rename option, you can change or rename the package name.
When you press F2, it will show you the dialog box as:
In this dialog, don't forget to check the "Update references" checkbox because by making "check" to t...
How to 'insert if not exists' in MySQL?
...
Solution:
INSERT INTO `table` (`value1`, `value2`)
SELECT 'stuff for value1', 'stuff for value2' FROM DUAL
WHERE NOT EXISTS (SELECT * FROM `table`
WHERE `value1`='stuff for value1' AND `value2`='stuff for value2' LIMIT 1)
Explanation:
The innermost query
SELECT *...
Select rows of a matrix that meet a condition
...20, ncol = 4)
colnames(m) <- letters[1:4]
The following command will select the first row of the matrix above.
subset(m, m[,4] == 16)
And this will select the last three.
subset(m, m[,4] > 17)
The result will be a matrix in both cases.
If you want to use column names to select columns...
Error while installing json gem 'mkmf.rb can't find header files for ruby'
...installing command-line tools and accepting the license with
sudo xcode-select --install
sudo xcodebuild -license accept
The issue is that Xcode 11 ships the macOS 10.15 SDK which includes headers for ruby2.6, but not for macOS 10.14's ruby2.3. You can verify that this is your problem by runnin...
How can I resolve “Error: No developer directory found at /Developer”?
...
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer
share
|
improve this answer
|
follow
...
CSS Child vs Descendant selectors
I am a bit confused between these 2 selectors.
8 Answers
8
...
CASCADE DELETE just once
...you want to cascade.
DELETE FROM some_child_table WHERE some_fk_field IN (SELECT some_id FROM some_Table);
DELETE FROM some_table;
share
|
improve this answer
|
follow
...