I have created a function in Postgresql and specified the returned type as TABLE (id uuid, data boolean).
This is the code that I have tried:
BEGIN
RETURN QUERY SELECT table.id, (table.data <> '') as data FROM table;
END
But it will return NULL for "data" when data is NULL in the table. I was expecting it to return FALSE.
Data column is storing a JSON and I am trying to check if the stored value is not null and not empty
How can I make this code work?
Use is distinct from to use a null-safe comparison:
SELECT table.id, table.data is distinct from '' as data
FROM table;
Another option is to treat an empty string like null:
SELECT table.id, nullif(table.data, '') is not null as data
FROM table;
Related
I am using sh2 function to generate the hash value but It is generating null/empty if any of the column value has null/empty.
For example
Input
select sha2(NULL, 256);
Output
NULL
is there any way to generate value even when the value inside sha2 function is empty/null.
NULL in SQL, means no value, so the result you are getting is expected.
You can create a query that will check for NULLs and return some predefined or random output for them, depending on what value you want, and the hash when there is the actual value. Example:
Create some test data:
create or replace table test_table (col1 string);
insert into test_table values ('string1'), (null), ('string2');
Return hash when it is not NULL
select
col1,
case
when col1 is null then 'value you want get instead of the hash'
else sha2(col1, 256)
end as result
from test_table;
Output:
Alternatively, you can output some random hash instead of a predefined string:
select
col1,
case
when col1 is null then sha2(random())
else sha2(col1, 256)
end as result
from test_table;
Output:
how do I insert the std_id value and sub_id value in the student_subject table
insert into student_subjects(student_id,subject_id)
values(std_id,(select id from subjects
where guid in
(select * from
unnest(string_to_array(subjects_colls,',')::uuid[])))::int);
ERROR: more than one row returned by a subquery used as an expression
Get rid of the values clause and use the SELECT directly as the source for the INSERT statement:
You also don't need to unnest your array, using = any() will be a bit more efficient (although I would recommend you do not pass comma separated strings, but an array of uuid directly)
insert into student_subjects(student_id,subject_id)
select std_id, s.id
from subjects s
where guid = any(string_to_array(subjects_colls,',')::uuid[])
I assume this is part of a procedure or function and std_id and subjects_colls are parameters passed to it.
I want to insert text data into a Postgres bytea column using the concat function or the || operator. I am getting an error
column "name" is of type bytea but expression is of type text
create table test(
name bytea
);
insert into test(name) values(concat('abac-' , 'test123'));
insert into test(name) values('aa' || 'bb');
I am executing the insert inside a stored procedure. If want to add the argument like
(concat('abac-' , row.name , 'test123'));
How do I do it?
Perform a type cast after concatenating the values:
INSERT INTO test (name)
VALUES (CAST('abac-' || row.name || 'test123' AS bytea));
Note: The difference between || and concat is how they behave with NULLs.
You need to cast both strings to bytea, for example:
insert into test(name) values('aa'::bytea || 'bb'::bytea);
I am new to PostgreSQL and trying to convert mssql scripts to Postgres.
For Merge statement, we can use insert on conflict update or do nothing but am using the below statement, not sure whether it is the correct way.
MSSQL code:
Declare #tab2(New_Id int not null, Old_Id int not null)
MERGE Tab1 as Target
USING (select * from Tab1
WHERE ColumnId = #ID) as Source on 0 = 1
when not matched by Target then
INSERT
(ColumnId
,Col1
,Col2
,Col3
)
VALUES (Source.ColumnId
,Source.Col1
,Source.Col2
,Source.Col3
)
OUTPUT INSERTED.Id, Source.Id into #tab2(New_Id, Old_Id);
Postgres Code:
Create temp table tab2(New_Id int not null, Old_Id int not null)
With source as( select * from Tab1
WHERE ColumnId = ID)
Insert into Tab1(ColumnId
,Col1
,Col2
,Col3
)
select Source.ColumnId
,Source.Col1
,Source.Col2
,Source.Col3
from source
My query is how to convert OUTPUT INSERTED.Id in postgres.I need this id to insert records in another table (lets say as child tables based on Inserted values in Tab1)
In PostgreSQL's INSERT statements you can choose what the query should return. From the docs on INSERT:
The optional RETURNING clause causes INSERT to compute and return value(s) based on each row actually inserted (or updated, if an ON CONFLICT DO UPDATE clause was used). This is primarily useful for obtaining values that were supplied by defaults, such as a serial sequence number. However, any expression using the table's columns is allowed. The syntax of the RETURNING list is identical to that of the output list of SELECT. Only rows that were successfully inserted or updated will be returned.
Example (shortened form of your query):
WITH [...] INSERT INTO Tab1 ([...]) SELECT [...] FROM [...] RETURNING Tab1.id
SELECT
Q."COLUMN1"
FROM
(SELECT
"COLUMN1",
CAST ((SELECT CAST (RTRIM (PARAM) AS VARCHAR(50)) FROM TABLE_VIEW WHERE PARAM_ID = :ID) AS VARCHAR(50)) AS "COLUMN2"
FROM ("TABLE1")Q
WHERE
RTRIM(CAST("COLUMN1" AS CHAR(10))) IN (SELECT VALUE_1 FROM TABLE (SPLIT_PARAMS(CAST(Q."COLUMN2" AS VARCHAR(50)),',',5)))
COLUMN2 gets its value from a separate table based on the input provided at run time.
The filter used in the query consists of a used defined table valued function that is used to split the comma separated valued to individual values.
The query throws the error message as:
"FUNCTION NOT SUPPORTED. SQLCODE=-270, SQLSTATE=42997"
Can anyone help me find the cause of the issue.