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Rename a class in Xcode: Refactor… is grayed out (disabled). Why?
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Select the class's symbol in its header file - i.e. the bit just after @interface. Then the refactoring stuff should be enabled.
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Query to count the number of tables I have in MySQL
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SELECT COUNT(*) FROM information_schema.tables WHERE table_schema = 'dbName';
Source
This is mine:
USE databasename;
SHOW TABLES;
SELECT FOUND_ROWS();
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What does SQL clause “GROUP BY 1” mean?
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SELECT account_id, open_emp_id
^^^^ ^^^^
1 2
FROM account
GROUP BY 1;
In above query GROUP BY 1 refers to the first column in select statement which is
account_id.
You also can speci...
How to select different app.config for several build configurations
...ctory. So if you had PatternPA.Test.Integration project and a Debug config selected, in the output folder after the build you will find a PatternPA.Test.Integration.dll.config file which was copied from Config\App.Debug.config and renamed afterwards.
These are some notes you can leave in the config...
SQL to find the number of distinct values in a column
I can select all the distinct values in a column in the following ways:
11 Answers
11
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Selecting last element in JavaScript array [duplicate]
...gth less 1.
Mozilla Docs on Slice
Performance of the various methods for selecting last array element
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Database Diagram Support Objects cannot be Installed … no valid owner
...rator and this has also invalidated the current owner of the database.
If SELECT @@SERVERNAME; is not accurate (it should say DevPC), then in order to ensure that your server rename has taken hold within SQL Server, you may also want to issue the following:
EXEC sp_dropserver @server = N'old serve...
SQL how to make null values come last when sorting ascending
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select MyDate
from MyTable
order by case when MyDate is null then 1 else 0 end, MyDate
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MySQL复制的概述、安装、故障、技巧、工具 - 数据库(内核) - 清泛网 - 专注...
...表可以使用不同的键类型。比如主服务器用InnoDB，键用VARCHAR的话节省空间，从服务器使用MyISAM，键用CHAR提高速度，因为MyISAM有静态表一说。
主从服务器中的表可以使用不同的索引。主服务器主要用来应付写操作，所以除了主...
COUNT DISTINCT with CONDITIONS
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You can try this:
select
count(distinct tag) as tag_count,
count(distinct (case when entryId > 0 then tag end)) as positive_tag_count
from
your_table_name;
The first count(distinct...) is easy.
The second one, looks somewhat complex...