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I have two tables
1. Named as t1
2. Named as t2

example of the tables are :

t1 :


 id  name 
 1   one 
 2   two 
 3   three  

t2 :


 id  name 
 2   five 

I need to select all the data from the t1 table as well as from table t2 but I don't want to write data from table t1 which is updated

I need a resulting table like this:


 id  name 
 1   one 
 2   five 
 3   three  

Please help me to solve this in postgres

0
SELECT
    t1.ID,
    CASE
WHEN t1."name" != t2."name" then
    t2.name
ELSE 
    t1.name
END as fname
FROM
    t1 LEFT JOIN t2 ON t1.ID = t2.ID

from comments - duplicates, mean You have duplicates (answer with coalesce return the same), variant for avoid duplicates:

SELECT T1.id,
       MAX(COALESCE(t2.name, t1.name)) as name
FROM t1
LEFT JOIN t2
     ON t1.id = t2.id
GROUP BY t1.id

but - be careful, which name You need to take? FIRST/MIN/MAX? because id=2, in t2 can have name = four/seven/eight ... which right?

  • it is giving me repetitive rows. for eg. same row 5 times – user3597719 Nov 19 '15 at 17:39
  • it always depend from You source data, which You not present, this is mean for each tow from t1 You've few row in t2. for avoid duplicates, You can add GROUP BY operation – a_vlad Nov 19 '15 at 17:45
4

The cleanest has to be:

SELECT T1.id
       COALESCE(t2.name, t1.name) as name
FROM t1
LEFT JOIN t2
     ON t1.id = t2.id

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