update statement with join and where clause-CodePudding

Working with some update and join statements from a previous code and trying to use spark sql statements to get the same result table 1

insert into tab1
VALUES(1, 'A1', 'B1', 1),
(2, 'A2', 'B2', 0),
(3, 'A3', 'B3',1 ),
(4, 'A4', 'B4',1 ),
(5, 'A5', 'B5',0 ),
(6, 'A6', 'B6',1 )
;

table 2

insert into tab2 
VALUES(1, 'A1', 'B1', 0),
(2, 'A2', 'B2', 1),
(3, 'A3', 'B3', 1),
(6, 'A6', 'B6', 0)
;

update statement

update tab1 
set v1 = concat(t1.v1,t2.v1)
from tab1 t1 
inner join tab2 t2 on t1.id =t2.id 
where t2.v3 > 0

Result table 1

1   A2A2    B1  1
2   A2A2    B2  0
3   A2A2    B3  1
4   A2A2    B4  1
5   A2A2    B5  0
6   A2A2    B6  1

Any idea why its not

1   A1      B1  1
2   A2A2    B2  0
3   A3A3    B3  1
4   A4      B4  1
5   A5      B5  0
6   A6      B6  1

CodePudding user response：

Get rid of the tab1 in the FROM clause and place tab2 instead. You can sort of do the join in the WHERE clause:

UPDATE tab1 t1
SET v1 = concat(t1.v1,t2.v1)
FROM tab2 t2 
WHERE t1.id =t2.id AND t2.v3 > 0;

CodePudding user response：

Turns out the previous code was running on MSSQL with the same syntax it gives the expected results after trying in a MSSQL server

1   A1      B1  1
2   A2A2    B2  0
3   A3A3    B3  1
4   A4      B4  1
5   A5      B5  0
6   A6      B6  1

in Postgresql the from_item as mentioned in the comment of this question Must not contain the same updated table!