如何在 MySQL 中选择非空列？
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How to select non-empty columns in MySQL?
提问by Nate
Sorry if this has been asked before, but I've been searching and can't find a solution to my simple problem.
抱歉，如果之前有人问过这个问题，但我一直在搜索，但找不到解决我的简单问题的方法。
I need to select all rows where a varchar column in it has text in it (letters, numbers, or special characters), so I wrote a query like the following:
我需要选择 varchar 列中包含文本（字母、数字或特殊字符）的所有行，因此我编写了如下查询：
SELECT col1
FROM table
WHERE col1 IS NOT NULL
But this returns columns that contain the value '' (i.e. it's blank, but is not set to NULL so it still gets returned).
但这会返回包含值 '' 的列（即它是空白的，但未设置为 NULL，因此它仍然会被返回）。
I tried changing the query to this:
我尝试将查询更改为：
SELECT col1
FROM table
WHERE col1 IS NOT NULL
AND col1 != ''
But that didn't work.
但这没有用。
How do I stop the rows where the column is blank from being returned?
如何阻止返回列为空白的行？
回答by Raab
use TRIMthere seems to be spaces in your column then
使用TRIM您的列中似乎有空格然后
SELECT col1
FROM table
WHERE col1 IS NOT NULL
AND TRIM(col1) <> ''
回答by Shankar Kalyankar
You can use this query if column is blank, but is not set to NULL
如果列为空但未设置为 NULL，则可以使用此查询
SELECT col1 FROM table where col1 not like '';# Two Single quotes without space
SELECT col1 FROM table where col1 not like '';# 两个没有空格的单引号
OR
或者
This if column has one or more spaces,
这如果列有一个或多个空格，
SELECT col1 FROM table where col1 not like '% %';
回答by sj59
use LENGTH:
使用LENGTH：
SELECT col1
FROM table
WHERE LENGTH(col1) > 0
