I have a column within a table of data type jsonb and another column of type bool.
I am looking to update the latter to true, else false, when the jsonb contains a value other than 'null' for certain attributes.
This is what I have so far.
update table
set bool_column =
case
when
jsonb_column->'term1' != 'null'
or jsonb_column->'term2' != 'null'
or jsonb_column->'term3' != 'null'
or jsonb_column->'term4' != 'null'
then true
else false;
I was able to figure out how to select the columns in the table but I can't figure out how to update a different column.
Your help would be much appreciated.
Thanks.
Related
I'm trying to update a bunch of jsonb values to null. Here's an example of what i'm trying to do and i'm getting the error below.
How can I set first-name to null in this case?
UPDATE users
SET
fields = fields || '{"first-name": NULL}'
WHERE user_id = 1;
ERROR: invalid input syntax for type json
LINE 3: fields = fields || '{"first-name": NULL}'
^
DETAIL: Token "NULL" is invalid.
CONTEXT: JSON data, line 1: {"first-name": NULL...
Use jsonb_set:
UPDATE users
SET
fields = jsonb_set(fields, '{first-name}', 'null')
WHERE user_id = 1;
If you want the null value inside the JSONB, then it must be a JSON null value, not an SQL NULL value. JSON null must be spelled in lower case.
I'm trying to update a nullable date column with NULL and for some reason Postgres takes NULL as text and gives the below error
UPDATE tbl
SET
order_date = data.order_date
FROM
(VALUES (NULL, 100))
AS data(order_date,id)
WHERE data.id = tbl.id
And the error shows:
[42804] ERROR: column "order_date" is of type date but expression is
of type text
Hint: You will need to rewrite or cast the expression.
I can fix this by explicitly converting NULL to date as below:
NULL::date
But, Is there a way to achieve this without explicit type conversion?
You can avoid the explicit cast by copying data types from the target table:
UPDATE tbl
SET order_date = data.order_date
FROM (
VALUES
((NULL::tbl).order_date, (NULL::tbl).id)
(NULL, 100)
) data(order_date, id)
WHERE data.id = tbl.id;
The added dummy row with NULL values is filtered by WHERE data.id = tbl.id.
Related answer with detailed explanation:
Casting NULL type when updating multiple rows
This question already has an answer here:
How to handle an optional value returned by a query using the postgres crate?
(1 answer)
Closed 5 years ago.
I am using the rust-postgres library and I want to do a SELECT and check if the first column of the first row is NULL or not.
This is how I get my data:
let result = connection.query(
r#"
SELECT structure::TEXT
FROM sentence
WHERE id = $1
"#,
&[&uuid]
);
let rows = result.expect("problem while getting sentence");
let row = rows
.iter()
.next() // there's only 1 result
.expect("0 results, expected one...");
The only simple way I found to figure it out is the following code:
match row.get_opt(0) {
Some(Ok(data)) => some data found,
Some(Err(_)) => the column is null,
None => out of bound column index
}
Unfortunately, it seems that Some(Err(_)) is the executed path for any kind of SQL/database error, and not only if the retrieved column is NULL.
Which condition should I use to check that the column is NULL ?
If all you need to know is whether the column is NULL, you could try changing your query to:
SELECT COUNT(1) FROM sentence WHERE id = $1 AND structure IS NOT NULL
with or without the NOT.
If you want to make the logic simpler so any error is an actual error, I'd consider changing the select value to something like:
COALESCE( structure::TEXT, ''::TEXT ) AS "structure"
so it should never be NULL. That should work as long as an empty string isn't a valid non-NULL value for that column.
Otherwise, I may have misunderstood your problem.
No version of a character varying field will return anything but NULL if there isn't a value... it's really frustrating
CASE WHEN COALESCE(NULLIF(e.name,''),'unassigned') IS NULL THEN 'unassigned' ELSE a.name END
was my final test and it still simply returns NULL unless the field has a value
it's character varying(255)
COALESCE(a.name,'unassigned') // won't work
NULLIF(a.name,'') // won't work
NULLIF(a.name,NULL) // won't work
COALESCE(NULLIF(a.name,''),'unassigned') // won't work
however the instant i use 0 it works..
what's up with that?
it's a character varying(255) field and it is set to default to null
as a matter of point the build of the table column is
name varying character(255) DEFAULT(NULL)
so I know it's entering NULL
and I've already done a
SELECT * FROM <tbl> WHERE name IS NULL; and of course, I return all the NULL rows with a.name... so what's the deal with this?
ok... to everyone deciding to answer me with:
COALESCE(NULLIF(e.name,''),'unassigned') IS NULL...
This method will never work on a return of "no records" and as this is a stored procedure which creates a materialized view, where I'm polling via nested queries - where it is possible for a column to have 0 (as the default id = other_id) the nested query would simply return no rows. When no row is returned, the functions of COALESCE or NULLIF would never execute. A row would have to be returned in order for those functions to act upon the row values... As I've never heard of a table with a PK auto-incremented field starting at 0 and generally starting at 1 the resultset of "no records returned" will always return a NULL value into the materialized view column.
The query I run afterward to poll rows from that materialized view will however function properly as COALESCE(etc etc) because now there is an actual NULL value in that column.
I'm writing some triggers to check if an arrtibute of a newly create tuple is present in another table. What is the best way to check this?
IF (SELECT * FROM TABLEB where NEW.Attribute = Attribute) = NULL THEN
return NULL
END IF
Is there a better way? And does a Select that returns nothing = NULL or empty set?
Use IF EXISTS (SELECT * FROM TABLEB where NEW.Attribute = Attribute).
An empty rowset isn't the same as NULL, which represents an empty cell of a row. Your syntax would only be valid if the query only selected one row, in which case PostgreSQL will allow use of comparison operators against the top cell returned, which counts as NULL if none are returned.