Am trying to convert below oracle query to postgres,
MERGE INTO table1 g
USING (SELECT distinct g.CDD , d.SGR
from table2 g, table3 d
where g.IDF = d.IDF) f
ON (g.SGR = f.SGR and g.CDD = f.CDD)
WHEN NOT MATCHED THEN
INSERT (SGR, CDD)
VALUES (f.SGR, f.CDD);
I made changes as below compatible to postgres:
WITH f AS (
SELECT distinct g.CDD , d.SGR
from table2 g, table3 d
where g.IDF = d.IDF
),
upd AS (
update table1 g
set
SGR = f.SGR , CDD = f.CDD
FROM f where g.SGR = f.SGR and g.CDD = f.CDD
returning g.CDD, g.SGR
)
INSERT INTO table1(SGR, CDD ) SELECT f.SGR, f.CDD FROM f;
But am doubtful ,my oracle query is not updating any columns if data matched , but am unable to convert it accordingly . Can anyone help me to correct it ?
Assuming you have a primary (or unique) key on (sgr, cdd) you can convert this to an insert ... on conflict statement:
insert into table1 (SGR, CDD)
select distinct g.CDD, d.SGR
from table2 g
join table3 d ON g.IDF = d.IDF
on conflict (cdd, sgr) do nothing;
If you don't have a unique constraint (which bears the question: why?) then a straight-forward INSERT ... SELECT statement should work (which would have worke in Oracle as well).
WITH f AS (
SELECT distinct g.CDD, d.SGR
from table2 g
join table3 d on g.IDF = d.IDF
)
INSERT INTO table1 (SGR, CDD)
SELECT f.SGR, f.CDD
FROM f
WHERE NOT EXISTS (select *
from table1 t1
join f on (t1.sgr, t1.cdd) = (f.cdd, f.sgrf));
Note that this is NOT safe for concurrent execution (and neither is Oracle's MERGE statement). You can still wind up with duplicate values in table1 (with regards to the combination of (sgr,cdd)).
The only sensible way to prevent duplicates is to create a unique index (or constraint) - which would enable you to use the much more efficient insert on conflict. You should really consider that if your business rules disallow duplicates.
Note that I converted your ancient, implicit join in the WHERE clause to a modern, explicit JOIN operator, but it is not required for this to work.
Related
I have a table, on which I have added a new column nxvl.
I need to do something like this
UPDATE table1
SET nxvl = nexval('my_sequence_1')
from table2
where table1.col_id = table2.id and table2.val_col=1
order by table1.date
UPDATE table1
SET nxvl = nexval('my_sequence_2')
from table2
where table1.col_id = table2.id and table2.val_col=2
order by table1.date
Postgres doesn't allow order by on update
It has around 100,000 rows.
Can it be done with Update command. Right now there are only 2 values in val_col ie 1 & 2
Since it's a one time thing, I don't mind doing it with functions and looping through each row and update.
For knowledge wondering if there's a better way of achieving it.
Using Postgres 12.2
You can set the order and fetch the associated sequence value in a subquery, then update table (without even considering the update order)
UPDATE table1
SET nxvl = a.seq
FROM
( select table1.id, nexval('my_sequence_1') seq
from table1
join table2
on table1.col_id = table2.id
and table2.val_col=1
order by table1.date
) a
WHERE table1.id = a.id;
I have two table with one of them is vertical i.e store only key value pair with ref id from table 1. i want to join both table and dispaly key value pair as a column in select. and also perform sorting on few keys.
T1 having (id,empid,dpt)
T2 having (empid,key,value)
select
T1.*,
t21.value,
t22.value,
t23.value,
t24.value
from Table1 t1
join Table2 t21 on t1.empid = t21.empid
join Table2 t22 on t1.empid = t22.empid
join Table2 t23 on t1.empid = t23.empid
where
t21.key = 'FNAME'
and t22.key = 'LNAME'
and t23.key='AGE'
The query you demonstrate is very inefficient (another join for each additional column) and also has a potential problem: if there isn't a row in T2 for every key in the WHERE clause, the whole row is excluded.
The second problem can be avoided with LEFT [OUTER] JOIN instead of [INNER] JOIN. But don't bother, the solution to the first problem is a completely different query. "Pivot" T2 using crosstab() from the additional module tablefunc:
SELECT * FROM crosstab(
'SELECT empid, key, value FROM t2 ORDER BY 1'
, $$VALUES ('FNAME'), ('LNAME'), ('AGE')$$ -- more?
) AS ct (empid int -- use *actual* data types
, fname text
, lname text
, age text);
-- more?
Then just join to T1:
select *
from t1
JOIN (<insert query from above>) AS t2 USING (empid);
This time you may want to use [INNER] JOIN.
The USING clause conveniently removes the second instance of the empid column.
Detailed instructions:
PostgreSQL Crosstab Query
I've seen a lot of post on multiple JOIN but it didn't help me in my case.
Consider that I have three tables and two cross-reference tables. That's the difference with the others posts where they had multiple tables but one cross-reference table in the FROM.
Table1 -> cross-ref1 <- table2 -> cross-ref2 <- table3
My version of Postgresql is : 9.0.11, and I'm working with W7 64 bits.
My request is the following stuff :
Select [columns] from cross-ref1, cross-ref2
INNER JOIN table1 ON table1.id_table1=cross-ref1.ref_id_table1
INNER JOIN table2 ON table2.id=cross-ref1.ref_id_table2
INNER JOIN table2 On table2.id_table2=cross-ref2.ref_id_table2
INNER JOIN table3 ON table3.id_table3=cross-ref2.ref_id_table3
The error message is : "Table name is specified more than once."
Can you explain me the error ?
Thanks
Cross-reference tables need separate columns for each side of the reference. An xref table with just one column makes no sense, as it can only refer to rows with the same ID on each side.
A typical setup would be:
CREATE TABLE a (
id integer primary key,
avalue text not null
);
CREATE TABLE b (
id integer primary key,
bvalue text not null
);
CREATE TABLE ab (
a_id integer references a(id),
b_id integer references b(id),
PRIMARY KEY(a_id, b_id)
);
Given sample data:
INSERT INTO a(id, avalue) VALUES
(1, 'a1'), (2, 'a2'), (3, 'a3'), (4, 'a4');
INSERT INTO b(id, bvalue) VALUES
(41, 'b1'), (42, 'b2'), (43, 'b3');
INSERT INTO ab(a_id, b_id) VALUES
(1, 41), (1, 42), (2, 43);
You'd find the pairings of a and b with:
SELECT avalue, bvalue
FROM a
INNER JOIN ab ON (a.id = ab.a_id)
INNER JOIN b ON (b.id = ab.b_id);
The crucial thing here is that you're joining on ab.a_id on the a side, and ab.b_id on the b side. Observe demo here: http://sqlfiddle.com/#!12/3228a/1
This is pretty much "many-to-many table relationships 101", so it might be worth doing some more study of introductory SQL and relational database tutorials and documentation.
You can't use the same table name twice (table2). In this case you need to use aliases like t1, t2a, t2b, ...
SELECT
...
FROM
table1 AS t1
INNER JOIN table2 AS t2a
ON t2a.id= ...
INNER JOIN table2 AS t2b
ON t2b.id= ...
INNER JOIN table3 AS t3
ON t3.id= ...
...
Now you can join whatever you want, how many times you want etc.
You have to explain what result you want to have. For example the following SQL is valid from syntax point of view, not sure about business point of view:
-- this will create sample data with 5 tables
with
crossref1(ref_id) as (VALUES (1),(2),(3)),
crossref2 (ref_id) as (VALUES (2),(3),(4)),
table1 (ref_id) as (VALUES (3),(4),(5)),
table2 (ref_id) as (VALUES (1),(2),(3)),
table3 (ref_id) as (VALUES (1),(2),(3))
-- valid SQL based on your example
select * from
crossref1
cross join crossref2
join table1 on table1.ref_id=crossref1.ref_id
join table2 as t2_1 on t2_1.ref_id=crossref1.ref_id
join table2 as t2_2 on t2_2.ref_id=crossref2.ref_id
join table3 on table3.ref_id=crossref2.ref_id
With your SQL there are two problems:
You have two references to table2, you have to add alias
You have to use cross join syntax instead of ,
If you would like to understand how with works (how I created sample data), PostgreSQL has excellent documentation on this.
I need help to optmize the SQL logic in one of my functions. Please, note that I am not able to use store procedure.
Here is my table. It will be initialized using #MainTable that contains a lot of records.
DECLARE TABLE #ResultTable
(
ResultValue INT
)
These are tables that stores some parameters - they can be emty too.
DECLARE TABLE #ParameterOne (ParameterOne INT)
DECLARE TABLE #ParameterTwo (ParameterOne NVARCHAR(100))
...
DECLARE TABLE #ParameterN(ParameterN TINYINT)
Now, I need to join a lot of tables to my #MainTable in order to select from it only some of its records.
The selected records depend on the information stored in the parameters table.
So, my current solution is:
INSERT INTO ResultTable(ResultValue)
SELECT ResultValue
FROM MainTable M
INNER JOIN #MainOne MO
ON M.ID=MO.ID
....
INNER JOIN #MainN MN
ON M.IDN=MN.ID
WHERE (EXISTS (SELECT 1 FROM #ParameterOne WHERE ParameterOne=MO.ID) OR NOT EXISTS (SELECT 1 FROM #ParameterOne))
AND
...
AND
(EXISTS (SELECT 1 FROM #ParameterN WHERE ParameterN=MN.Name) OR NOT EXISTS (SELECT 1 FROM #ParameterN ))
So, the idea is to add the records only if they match the current criteria from the parameters tables.
Because I am not able to use procedure to build dynamic query I am using the WHERE clause with combinations of EXISTS and NOT EXISTS for each parameter table.
The problem is that it works slower when I am adding more and more parameters table. Is there an other way to do this without using a lot of IF/ELSE statements checking what parameter table has records - it will make the function a lot bigger and difficult for read.
And ideas and advices are welcomed.
Good question.
Try the following one:
INSERT INTO ResultTable(ResultValue)
SELECT ResultValue
FROM MainTable M
INNER JOIN (SELECT * FROM #MainOne WHERE (EXISTS (SELECT 1 FROM #ParameterOne WHERE ParameterOne=#MainOne.ID) OR NOT EXISTS (SELECT 1 FROM #ParameterOne))) MO
ON M.ID=MO.ID
....
INNER JOIN (SELECT * FROM #MainN WHERE (EXISTS (SELECT 1 FROM #ParameterN WHERE ParameterOne=#MainN.Name OR NOT EXISTS (SELECT 1 FROM #ParameterN))) MO
ON M.IDN=MN.ID
Advantages:
Result of the JOIN is more quickly, because it does not process all data (it is already filtered)
It looks more simple for adjusting
I have two tables say Table1 and Table2 that contains the following column with which I should join and perform an update a column of Table1 with the value of the same column present in Table2.
Columns for Join condition:
Table1.mem_ssn and Table2.ins_ssn
Table1.sys_id and Table2.sys_id
Table1.grp_id and Table2.grp_id
Column to update:
Table1.dtofhire=Table2.dtofhire
I need a way to bulk update (using single update query without looping) the above mentioned column in Oracle 11G.
Table1 does not contain any key constraint specified since it will be used as a staging table for Data upload.
Please help me out to update the same.
You can use the MERGE statement.
It should look something like this:
MERGE INTO table1 D
USING (SELECT * FROM table2 ) S
ON (D.mem_ssn = S.ins_ssn and D.sys_id = S.sys_id and D.grp_id=S.grp_id)
WHEN MATCHED THEN
UPDATE SET D.dtofhire=S.dtofhire;
UPDATE:
Since you have more than one row in table2 with the same (ins_ssn,sys_id,grp_id) and you want the max dtofhire, you should change the query in the using clause:
MERGE INTO table1 D
USING (SELECT ins_ssn, sys_id, grp_id, max(dtofhire) m_dtofhire
FROM table2
GROUP BY ins_ssn,sys_id,grp_id) S
ON (D.mem_ssn = S.ins_ssn and D.sys_id = S.sys_id and D.grp_id=S.grp_id)
WHEN MATCHED THEN
UPDATE SET D.dtofhire=S.m_dtofhire;
The query that I used to arrive the functionality is seen below
UPDATE table1 T2
SET dtofhire = (SELECT Max(dtofhire) AS dtofhire
FROM table2 T1
WHERE T2.mem_ssn = T1.ins_ssn
AND T2.sys_id = T1.sys_id
AND T2.grp_id = T1.grp_id
GROUP BY ins_ssn,
sys_id,
grp_id)
WHERE ( mem_ssn, sys_id, grp_id ) IN (SELECT ins_ssn,
sys_id,
grp_id
FROM table2 );