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Detect if value is number in MySQL
...
This should work in most cases.
SELECT * FROM myTable WHERE concat('',col1 * 1) = col1
It doesn't work for non-standard numbers like
1e4
1.2e5
123. (trailing decimal)
share
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Find rows that have the same value on a column in MySQL
...sses and how many times they're used, with the most used addresses first.
SELECT email,
count(*) AS c
FROM TABLE
GROUP BY email
HAVING c > 1
ORDER BY c DESC
If you want the full rows:
select * from table where email in (
select email from table
group by email having count(*) &g...
What is the error “Every derived table must have its own alias” in MySQL?
...er), which can the be used to refer to it in the rest of the outer query.
SELECT ID FROM (
SELECT ID, msisdn FROM (
SELECT * FROM TT2
) AS T
) AS T
In your case, of course, the entire query could be replaced with:
SELECT ID FROM TT2
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Consistency of hashCode() on a Java string
....x the hashCode
function for long Strings worked by
sampling every nth character. This
pretty well guaranteed you would have
many Strings hashing to the same
value, thus slowing down Hashtable
lookup. In JDK 1.2 the function has
been improved to multiply the result
so far by 31 then ...
How do I run Visual Studio as an administrator by default?
...indows 8, 8.1 and 10
In Windows 8, you have to right-click devenv.exe and select "Troubleshoot compatibility".
Select "Troubleshoot program"
Check "The program requires additional permissions"
click "Next", click "Test the program..."
Wait for the program to launch
Click "Next"
Select "Yes, save ...
Removing duplicate rows from table in Oracle
...
Use the rowid pseudocolumn.
DELETE FROM your_table
WHERE rowid not in
(SELECT MIN(rowid)
FROM your_table
GROUP BY column1, column2, column3);
Where column1, column2, and column3 make up the identifying key for each record. You might list all your columns.
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SQL Server loop - how do I loop through a set of records
how do I loop through a set of records from a select?
8 Answers
8
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OceanBase使用libeasy原理源码分析：客户端 - 数据库(内核) - 清泛网 - 专...
...个session只封装一个请求
easy_request_t r;
char data[0];
};
libeasy作为客户端时，将每个发往libeasy服务器端的请求包封装成一个session(easy_session_t)，客户端将这个session放入连接的队列中然后返回，随后...
PhpStorm wrap/surround selection?
... to wrap a certain part of text. Is there any shortcut to wrap the current selection, for example:
4 Answers
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How do I wrap a selection with an HTML tag in Visual Studio?
...Studio 2015 comes with a new shortcut, Shift+Alt+W, that wraps the current selection with a div. This shortcut leaves the text "div" selected, making it seamlessly changeable to any desired tag. This coupled with the automatic end tag replacement makes for a quick solution.
UPDATE
This shortcut is a...