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Mathematical functions in Swift
... sqrt, floor and round because you may natively use respectively 0.5.squareRoot(), Int(0.5) and 0.5.round().
– Cœur
Oct 10 '18 at 10:04
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Reason for Column is invalid in the select list because it is not contained in either an aggregate f
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@davidblaine, MySQL has a function GROUP_CONCAT() for that. dev.mysql.com/doc/refman/5.5/en/… But in standard SQL, each column should contain only one value. That's fundamental to relational theory too.
– Bill Kar...
Unknown Column In Where Clause
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See the following MySQL manual page: http://dev.mysql.com/doc/refman/5.0/en/select.html
"A select_expr can be given an alias
using AS alias_name. The alias is used
as the expression's column name and
can be used in GROUP BY, ORDER BY...
mysql command for showing current configuration variables
Can not find a command that displays the current configuration of mysql from within the database.
3 Answers
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iOS开发调试技巧总结 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...复杂。这样就给我们新接手项目的开发者带来很多困扰。如何快速查看一个复杂UI的界面层次和布局，最快的方法就是用到视图调试。
当项目运行到某一个界面（可以是模拟器或真机）时，开启视图调试，点击按钮如图：
这样...
What is the difference between single and double quotes in SQL?
...ct_id
SELECT PRODUCT.id 'product_id'
Either works in Oracle, SQL Server, MySQL… but I know some have said that the TOAD IDE seems to give some grief when using the single quotes approach.
You do have to use single quotes when the column alias includes a space character, e.g., product id, but it...
NPM cannot install dependencies - Attempt to unlock something which hasn't been locked
...t the problem was. My ".npm" folder in my home directory was owned by the root user instead of myself. I'm not sure what happened to cause that. Maybe I installed node or npm as the root admin at one point. In any case I just ran sudo chown -R [username] .npm and I was finally able to run npm in...
How to get ER model of database from server with Workbench
...y to get an ER model of a database from the server that is connected to my MySQL Workbench?
4 Answers
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MySQL Select Query - Get only first 10 characters of a value
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Using the below line
SELECT LEFT(subject , 10) FROM tbl
MySQL Doc.
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MySQL, better to insert NULL or empty string?
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Better to Insert NULL for consistency in your database in MySQL. Foreign keys can be stored as NULL but NOT as empty strings.
You will have issues with an empty string in the constraints.
You may have to insert a fake record with a unique empty string to satisfy a Foreign Key cons...