return a boolean using Postgres - postgresql

How to return a boolean true/false instead of t/f from a field of string type in Postgres.
SELECT (CASE WHEN status = 'active' THEN true ELSE false END)::boolean AS status
FROM table;


t and f is just how psql prints booleans, it shouldn't be important. Also, you can simplify your query as follows:
SELECT status = 'active' AS status FROM table;
If you really want to get text for the column status, do the following:
SELECT (status = 'active')::text AS status FROM table;
If you want to get a number instead (0 for false, 1 for true), do this:
SELECT (status = 'active')::integer AS status FROM table;

Related

Update jsonb set new value select from the same table

i have a table foo:
id | items
---+--------------------------------
1 |{"item_1": {"status": "status_1"}}
2 |{"item_2": {"status": "status_2"}}
...
I need to update all rows in column items which is a jsonb and set after {"status": "status"} new values ("new_value": "new_value") and after update the result must look like this:
id | items
---+------------------------------------------------------------
1 |{"item_1": {"status": "status_1", "new_value": "new_value"}}
2 |{"item_2": {"status": "status_2", "new_value": "new_value"}}
...
i've tried to do this:
WITH result AS (
INSERT INTO foo (id, items)
SELECT id, options || newvalue as res
FROM foo AS bar,
jsonb_each(bar.items::jsonb) AS item,
to_jsonb(item.value) AS options,
jsonb_build_object('new_value', 'new_value') as newvalue
WHERE id IN ('1', '2'...)
ON CONFLICT (id)
DO UPDATE
SET items = foo.items || Excluded.items::jsonb RETURNING *)
SELECT item.key AS itemkey
FROM result AS res,
jsonb_each(res.items) AS item,
to_jsonb(item.value) AS options;
but when i run this script the postgres shows this error message:
on conflict do update command cannot affect row a second time postgres
i dont understand what am i doing wrong?
UPDATE#1
Postgres version 9.6
table foo id = TEXT UNIQUE NOT NULL
about why INSERT but not just UPDATE? the answer is this is my mistake first mistake.

after some reading postgres functions finally i find out:
UPDATE foo as t
SET items = result.new_value
FROM (SELECT st.id, new_value
FROM foo AS st
CROSS JOIN LATERAL (
SELECT jsonb_object_agg(the_key, the_value || '{"new_value": "some_new_value"}'::jsonb) AS new_value
FROM jsonb_each(st.items) AS x(the_key, the_value)
LIMIT 1) AS n) AS result
WHERE result.id = t.id;

Eloquent how to return null

I have the following query:
SELECT null as id, null as cost, null as title FROM books LIMIT 1
It returns one single record.
Using Eloquent, I've tried
$listagem = Book::where('id','=',-1)->get();// there is no id = -1
$listagem = Livro::select('NULL as id' ,'NULL as cost', 'NULL as title')->get();
(...)
but nothing works.
What is the correct sintax?
Thanks

INSERT INTO not working in IF block - T-SQL

im working on procedure which should transfer number of items (value #p_count) from old store to new store
SET #countOnOldStore = (SELECT "count" FROM ProductStore WHERE StoreId = #p_oldStoreId AND ProductId = #p_productID)
SET #countOnNewStore = (SELECT "count" FROM ProductStore WHERE StoreId = #p_newStoreID AND ProductId = #p_productID)
SET #ShiftedCount = #countOnOldStore - #p_count
SET #newStoreAfterShift = #countOnNewStore + #p_count
IF #ShiftedCount > 0
BEGIN
DELETE FROM ProductStore WHERE storeId = #p_oldStoreId and productID = #p_productID
INSERT INTO ProductStore (storeId,productId,"count") VALUES (#p_oldStoreId,#p_productID,#ShiftedCount)
DELETE FROM ProductStore WHERE storeId = #p_newStoreID and productID = #p_productID
INSERT INTO ProductStore (storeId,productId,"count") VALUES (#p_newStoreID,#p_productID,#newStoreAfterShift)
END
ELSE
PRINT 'ERROR'
well ... second insert is not working. I cant figure it out. It says
Cannot insert the value NULL into column 'count', table 'dbo.ProductStore'; column does not allow nulls. INSERT fails.
Can anyone see problem and explain it to me ? Its school project

It looks like your entire query should just be:
UPDATE ProductStore
SET [count] = [count] + CASE
WHEN storeId = #p_NewStoreID THEN #p_Count
ELSE -#p_Count END
WHERE
productID = #p_ProductID and
storeID in (#p_NewStoreID,#p_OldStoreID)

If either value in the following is NULL, the total will be NULL:
SET #newStoreAfterShift = #countOnNewStore + #p_count
Check both values (#countOnNewStore, #p_count) for NULL.

Looks like you are not assigning any value to #p_count, so it is NULL and so are #ShiftedCount and #newStoreAfterShift.

DB2 Merge using multiple columns in ON statement

I have a megre statement that does something like the following:
MERGE INTO TABLE_NAME1 tgt
USING (SELECT CONTRACTOR, TRACTOR, COL1, COL2 FROM TABLE_NAME2) src
ON src.CONTRACTOR = tgt.CONTRACTOR AND src.TRACTOR = tgt.TRACTOR
This is because a contractor can have multiple tractors. The table key is not used because it is an identity key only - auto number on insert.
The Merge runs OK when the table is empty, but when running it again it duplicates the rows where the tractor is null. So I tried:
ON ((src.CONTRACTOR = tgt.CONTRACTOR AND src.TRACTOR = tgt.TRACTOR)
OR (src.CONTRACTOR = tgt.CONTRACTOR AND tgt.TRACTOR IS NULL))
But this causes it to hang. Does DB2 have an issue comparing NULL to NULL?

"Does DB2 have an issue comparing NULL to NULL?" No, it does not. However, the result of such a comparison is unknown, in other words, it is neither true nor false:
$ db2 "select * from sysibm.sysdummy1"
IBMREQD
-------
Y
1 record(s) selected.
$ db2 "select * from sysibm.sysdummy1 where null = null"
IBMREQD
-------
0 record(s) selected.
$ db2 "select * from sysibm.sysdummy1 where null != null"
IBMREQD
-------
0 record(s) selected.
Without seeing your complete statement and sample data it's hard to provide a definite answer, but you may want to try instead:
...ON ((src.CONTRACTOR = tgt.CONTRACTOR AND src.TRACTOR = tgt.TRACTOR
AND tgt.TRACTOR IS NOT NULL))

Select a string comparison as a boolean in tsql

In a tsql query, I want to have a calculated field that is the boolean result of a string comparison.
It would look something like this:
select name, (status = 'current') as IsValid
from items
But the query as I have listed is not valid. What is the correct syntax?

I would use a case statement
Select name, case when status = 'current' then 1 else 0 end as IsValid
from items

Try this -
select name,
(CASE status WHEN 'current' THEN 1 Else 0 END) as IsValid
from items

select name, IIF(status = 'current', 1, 0) as IsValid
from items