I have a view and two tables. Tables one and two have the same columns, but table one is has as small number of records, and table two has old data and a huge number of records.
I have to join a view with these two tables to get the latest data from table one; if a record from the view is not available in table one then I have to select the record from table two.
How can i achieve this with MySQL?
I came to know by doing some research in internet that we can't apply full join and sub query in from clause.
Just do a simple UNION of the results excluding the records in table2 that are already mentioned in table1:
SELECT * FROM table1
UNION
SELECT * FROM table2
WHERE NOT EXISTS (SELECT * FROM table1 WHERE table2.id = table1.id)
Something like this.
SELECT *
FROM view1 V
INNER JOIN (SELECT COALESCE(a.commoncol, b.commoncol) AS commoncol
FROM table1 A
FULL OUTER JOIN table2 B
ON A.commoncol = B.commoncol) C
ON v.viewcol = c.commoncol
If you are using Mysql then check here to simulate Full Outer Join in MySQL
are you trying to update the view from two tables where old record in view needs to be overwritten by latest/updated record from table1 and non existant records from table1 to be appended from table2?
, or are you creating a view from two tables?
Related
I am using PGAdmin III and postgres 9.6
I have postgres schemas that consists of 250 tables with various columns. Two tables are of similar names and have the same columns, but unique data and IDs. I want to UPDATE one column in both tables with a specific number but choosing which rows get updated is complicated.
I have a script which correctly works on one table at a time, but I wonder if it can be done in a single script. I have tried using DO and LOOP but keep running into roadblocks.
Here's the working single-table script:
UPDATE table1
SET number = 44
WHERE table1.id IN
(SELECT table1.id FROM plan
JOIN name ON name.id = plan.nameid
JOIN type ON type.id = name.typeid
JOIN simul ON simul.id = plan.simulid
LEFT JOIN table1 ON table1.id = tableid
WHERE type.tag = 'X' AND plan.class LIKE '%Table%' AND simul.label IN
('SIMUL90','SIMUL99','SIMUL87'));
"plan.class" contains text which determines class of simul and thus either Table1 or Table2. Table1 and Table2 are of identical column structure but their IDs may be identical so UNION is out of consideration. TH other joins are to fine tune the SELECT so I get only a small subset of the table. The number to update is the same for either table.
I'm joining different tables with countries information, where one of them (cty) is the main table with the countries' names. All the tables have a column c, linking to the primary key in cty (also called c).
To join them all, I first used
select * from cty
full join table1 using (c)
full join table2 using (c)
This gives me all the countries in cty, but I want only the countries present in the other tables. To solve this, I tried
select * from table1
full join table2 using (c)
join cty using (c)
This solves the problem about the number of lines, but now the main columns are the last in the table.
Is there a way to keep the columns from cty in the beginning (left side) of the table without specifying all the column names of all tables (I have many tables), and keep only the lines present in the secondary tables?
select * from cty
right join
(select * from table1
full join table2 using(id)
) fj on fj.id = tt1.id
;
Check it: http://rextester.com/HCA83570
I'm trying to implement a many-to-many relationship using PostgreSQL's Array type, because it scales better for my use case than a join table would. I have two tables: table1 and table2. table1 is the parent in the relationship, having the column child_ids bigint[] default array[]::bigint[]. A single row in table1 can have upwards of tens of thousands of references to table2 in the table1.child_ids column, therefore I want to try to limit the amount returned by my query to a maximum of 10. How would I structure this query?
My query to dereference the child ids is SELECT *, json_agg(table2.*) as children FROM table1 INNER JOIN table2 ON table2 = ANY(table1.child_ids). I don't see a way I could set a limit without limiting the entire response as a whole. Is there a way to either limit this INNER JOIN, or at least utilize a subquery to that I can use LIMIT to restrict the amount of results from table2?
This would have been dead simple with properly normalized tables, but here goes with arrays:
SELECT *
FROM table1 t1, LATERAL (
SELECT json_agg(*) AS children
FROM table2
WHERE id = ANY (t1.child_ids)
LIMIT 10) t2;
Of course, you have no influence over which 10 rows per id of table2 will be selected.
I am new to postgresql (and databases in general) and was hoping to get some pointers on improving the efficiency of the following statement.
I am inserting data from one table to another, and do not want to insert duplicate values. I have a rid (unique identifier in each table) that are indexed and are Primary Keys.
I am currently using the following statement:
INSERT INTO table1 SELECT * FROM table2 WHERE rid NOT IN (SELECT rid FROM table1).
As of now the table one is 200,000 records, table2 is 20,000 records. Table1 is going to keep growing (probably to around 2,000,000) and table2 will stay around 20,000 records. As of now the statement takes about 15 minutes to run. I am concerned that as Table1 grows this is going to take way to long. Any suggestions?
This should be more efficient than your current query:
INSERT INTO table1
SELECT *
FROM table2
WHERE NOT EXISTS (
SELECT 1 FROM table1 WHERE table1.rid = table2.rid
);
insert into table1
select t2.*
from
table2 t2
left join
table1 t1 on t1.rid = t2.rid
where t1.rid is null
I need to perform distinct select on few columns out of which, one column is non-distinct. Can I specify which columns make up the distinct group in my SQL statement.
Currently I am doing this.
Select distinct a,b,c,d from TABLE_1 inner join TABLE_2 on TABLE_1.a = TABLE_2.a where TABLE_2.d IS NOT NULL;
The problem I have is I am getting 2 rows for the above SQL because column D holds different values. How can I form a distinct group of columns (a,b&c) ignoring column d, but have column d in my select clause as well?
FYI: I am using DB2
Thanks
Sandeep
SELECT a,b,c,MAX(d)
FROM table_1
INNER JOIN table_2 ON table_1.a = table_2.a
GROUP BY a,b,c
Well, your question, even with refinements, is still pretty general. So, you get a general answer.
Without knowing more about your table structure or your desired results, it may be impossible to give a meaningful answer, but here goes:
SELECT a, b, c, d
FROM table_1 as t1
JOIN table_2 as t2
ON t2.a = t1.a
AND t2.[some_timestamp_column] = (SELECT MAX(t3.[some_timestamp_column])
FROM table_2 as t3
WHERE t3.a = t2.a)
This assumes that table_1 is populated with single rows to retrieve, and that the one-to-many relationship between table_1 and table_2 is created because of different values of d, populated at unique [some_timestamp_column] times. If this is the case, it will get the most-recent table_2 record that matches to table_1.