大约有 40,000 项符合查询结果（耗时：0.0419秒） [XML]
How to use NULL or empty string in SQL
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Select *
From Table
Where (col is null or col = '')
Or
Select *
From Table
Where IsNull(col, '') = ''
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improve t...
Multiple select statements in Single query
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SELECT (
SELECT COUNT(*)
FROM user_table
) AS tot_user,
(
SELECT COUNT(*)
FROM cat_table
) AS tot_cat,
(
SELECT COUNT(*)
FROM course_table
) AS tot_course
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LISTAGG in Oracle to return distinct values
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19c and later:
select listagg(distinct the_column, ',') within group (order by the_column)
from the_table
18c and earlier:
select listagg(the_column, ',') within group (order by the_column)
from (
select distinct the_column
from t...
Check if table exists without using “select from”
Is there a way to check if a table exists without selecting and checking values from it?
17 Answers
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SQL statement to select all rows from previous day
I am looking for a good SQL Statement to select all rows from the previous day from one table. The table holds one datetime column. I am using SQL Server 2005.
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MySQL SELECT only not null values
Is it possible to do a select statement that takes only NOT NULL values?
9 Answers
9
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How to remove the arrow from a select element in Firefox
I'm trying to style a select element using CSS3. I'm getting the results I desire in WebKit (Chrome / Safari), but Firefox isn't playing nicely (I'm not even bothering with IE). I'm using the CSS3 appearance property, but for some reason I can't shake the drop-down icon out of Firefox.
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Simplest way to do a recursive self-join?
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WITH q AS
(
SELECT *
FROM mytable
WHERE ParentID IS NULL -- this condition defines the ultimate ancestors in your chain, change it as appropriate
UNION ALL
SELECT m.*
FROM mytable m
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Select2 dropdown but allow new values by user?
I want to have a dropdown with a set of values but also allow the user to "select" a new value not listed there.
9 Answers...
Simple way to calculate median with MySQL
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In MariaDB / MySQL:
SELECT AVG(dd.val) as median_val
FROM (
SELECT d.val, @rownum:=@rownum+1 as `row_number`, @total_rows:=@rownum
FROM data d, (SELECT @rownum:=0) r
WHERE d.val is NOT NULL
-- put some where clause here
ORDER BY d.val
) ...