postgresql 是否可以在 SQL 中将布尔值转换为字符串？
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Is it possible to convert a boolean to a string in SQL?
提问by user8659376
I have a column called live_in_citythat provides a boolean value. I want to convert it to a string though.
我有一个名为的列live_in_city，它提供一个布尔值。不过我想将其转换为字符串。
I tried using cast((live_in_city) as varchar(256)), but it says cannot cast type boolean to character varying.
我尝试使用cast((live_in_city) as varchar(256))，但它说不能将类型布尔值转换为字符变化。
Is there another way of doing this?
有没有其他方法可以做到这一点？
采纳答案by Raj
Try using below. Here you can assign value to 1 and 0 . then convert that.
尝试使用下面。在这里，您可以为 1 和 0 赋值。然后转换那个。
Select
Cast(Case
When live_in_city=1 Then 'True'
ELse 'False' END
AS Varchar(256))
from #t
The above works if live_in_cityis a number (integer, numeric, ...).
如果live_in_city是数字（整数，数字，...），则上述方法有效。
For a real booleancolumn, the following should be used:
对于真正的boolean列，应使用以下内容：
Select Case
When live_in_city Then 'True'
ELse 'False'
END
from the_table;
回答by clemens
Casting to TEXTworks fine for me in Postgres 9.5:
铸造到TEXT了在Postgres 9.5正常工作对我说：
# select (0 = 0)::TEXT, (0 = 1)::TEXT;
text | text
------+-------
true | false
(1 row)
and also your code works as well:
并且您的代码也能正常工作：
# SELECT cast((1 = 1) as varchar(256)), cast((1 = 0) as varchar(256));
varchar | varchar
---------+---------
true | false
(1 row)
Note: (1 = 1)and (1 = 0)are placeholders for all possible expressions, that returning trueor false.
注意：(1 = 1)and(1 = 0)是所有可能的表达式的占位符，返回true或false。
回答by Harald Nordgren
You can cast it to text like this:
您可以将其转换为这样的文本：
CAST(table.column AS TEXT)
