PostgreSQL boolean comparison

Question

Is there a difference in the following comparisons

#1

where x = true

#2

where x is true

#3

where x = '1'

#4

where x

user_6464308 · Answer

This is exactly the same as
```
WHERE x
```
It is TRUE, FALSE or NULL exactly when x is.
This is the same as the first case, except when x is NULL, in which case it will be FALSE. So it is the same as
```
WHERE coalesce(x, FALSE)
```
This happens to be the same as the first case, since '1' is interpreted as TRUE. See the documentation:

The datatype input function for type boolean accepts these string representations for the “true” state:

true
yes
on
1

My preferred way is the simplest:

WHERE x

user_7635569 · Answer

Using is or is not will handle the case when the value is null. If you rely on =, the result of the comparison will also be null

select null is true as "is", null = true as "equal";
 is | equal
----+-------
 f  |
(1 row)