大约有 47,000 项符合查询结果（耗时：0.0403秒） [XML]
Get top n records for each group of grouped results
...ould need to specify the group number and add queries for each group:
(
select *
from mytable
where `group` = 1
order by age desc
LIMIT 2
)
UNION ALL
(
select *
from mytable
where `group` = 2
order by age desc
LIMIT 2
)
There are a variety of ways to do this, see this articl...
Using column alias in WHERE clause of MySQL query produces an error
... though, by putting the expression directly into the WHERE x IN y clause:
SELECT `users`.`first_name`,`users`.`last_name`,`users`.`email`,SUBSTRING(`locations`.`raw`,-6,4) AS `guaranteed_postcode`
FROM `users` LEFT OUTER JOIN `locations`
ON `users`.`id` = `locations`.`user_id`
WHERE SUBSTRING(`loca...
How can I combine multiple rows into a comma-delimited list in Oracle? [duplicate]
...countries values ('Andorra');
insert into countries values ('Antigua');
SELECT SUBSTR (SYS_CONNECT_BY_PATH (country_name , ','), 2) csv
FROM (SELECT country_name , ROW_NUMBER () OVER (ORDER BY country_name ) rn,
COUNT (*) OVER () cnt
FROM countries)
WHE...
How to best display in Terminal a MySQL SELECT returning too many fields?
...
Terminate the query with \G in place of ;. For example:
SELECT * FROM sometable\G
This query displays the rows vertically, like this:
*************************** 1. row ***************************
Host: localhost
Db: mydatabase1
...
MySQL “NOT IN” query
...
To use IN, you must have a set, use this syntax instead:
SELECT * FROM Table1 WHERE Table1.principal NOT IN (SELECT principal FROM table2)
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MFC CListCtrl使用方法详解 - C/C++ - 清泛网 - 专注C/C++及内核技术
...DWORD dwStyle = m_list.GetExtendedStyle();
dwStyle |= LVS_EX_FULLROWSELECT;//选中某行使整行高亮（只适用与report风格的listctrl）
dwStyle |= LVS_EX_GRIDLINES;//网格线（只适用与report风格的listctrl）
dwStyle |= LVS_EX_CHECKBOXES;//item前生成checkbox...
typecast string to integer - Postgres
...ur value is an empty string, you can use NULLIF to replace it for a NULL:
SELECT
NULLIF(your_value, '')::int
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How do I query between two dates using MySQL?
...ember 29 2010 and January 30 2010). Try reversing the order of the dates:
SELECT *
FROM `objects`
WHERE (date_field BETWEEN '2010-01-30 14:15:55' AND '2010-09-29 10:15:55')
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Row count with PDO
...
$sql = "SELECT count(*) FROM `table` WHERE foo = ?";
$result = $con->prepare($sql);
$result->execute([$bar]);
$number_of_rows = $result->fetchColumn();
Not the most elegant way to do it, plus it involves an extra query...
MySQL Select all columns from one table and some from another table
How do you select all the columns from one table and just some columns from another table using JOIN? In MySQL.
4 Answers
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