I have two tables.
Table 1
Id
UpdateId
Name
Table 2
Table1ID
UpdateID
Address
Each time user update, system will insert record to table1. But for table2, system only insert record when there is update in address.
Sample data
Table 1
1,1,name1
1,2,name1
1,3,name1update
1,4,name1update
1,5,name1
1,6,name2
Table 2
1,1,address
1,4,addressupdate
I want to get the result as following
1,1,name1,address
1,2,name1,address
1,3,name1update,address
1,4,name1update,addressupdate
1,5,name1,addressupdate
1,6,name2,addressupdate
How to make use of join condition to achieve as above?
You can use a correlated subquery. Here is standard syntax, but it can be easily adapted to any database:
select t1.*,
(select t2.addressid
from table2 t2
where t2.table1id = t1.id and
t2.updateid <= t1.updateid
order by t2.updateid desc
fetch first 1 row only
) as addressid
from table1 t1;
you can use left join when you want to take all columns from left table t1 even though it doesn't match with the other table with column updateid on t2 table.
select t1.id,t1.updateid,t1.name,t2.address from table1 t1
left join table2 t2
on t2.updateid= t1.updateid
you can read more about joins here
Related
I have two tables and i want to use some records from first table and get last related record from another one.
You can see my tables
I want to join table 1 with last record of table 2. (creationDate = 2018-07-20)
If you simply want to get the latest record in table 2 for every ID in table one then this will work:
select t1.ID, t1.Name, q.ID, q.CreationDate
from table1 t1
outer apply
(
select top 1 t2.ID, t2.CreationDate
from table2 t2
where t2.tbl_1_Id = t1.ID
order by t2.CreationDate desc
)q
I want to get a value from an IN subquery with two columns, without needing to do two queries.
Sample:
SELECT * FROM table1 WHERE id IN(SELECT id, flags FROM table2);
Now I want to get flags directly. Is it possible, and if yes, how?
Any help is appreciated :)
It sounds like you are trying to achieve one of two things:
1) Select every field of records in table1 (and the associated table 2 flag) where the record's id is also found in the id column of table2. If that is the case, then yes, a join will accomplish what you want:
SELECT t1.*,
t2.flags
FROM table1 t1
JOIN table2 t2
ON t1.id = t2.id;
Note that JOIN is used here (rather than other types of joins such as LEFT JOIN) because JOIN will return only table1 records with a match in table2.id. LEFT JOIN, on the other hand, would return every table1 record, and table1 ids without a match in table2 would simply have null in the flags column of your returned table.
2) Select every field of records in table1 where the record's id is also found in either the id column of table2 or the flags column of table2. If that is the case, there are a few ways you could get the desired result, but achieving this using a subquery similar to the question
SELECT *
FROM table1
WHERE id IN (SELECT id FROM table2 UNION DISTINCT SELECT flags FROM table2)
You do this using join:
SELECT t1.*, t2.flags
FROM table1 t1 JOIN
table2 t2
ON t1.id = t2.id;
I want to delete an entry in a table where multiple fields match the results of another select subquery which takes data from another table.
query :
DELETE FROM table1
WHERE carriedby_circuit IN (SELECT
circuit_id
FROM table2
WHERE circuit_name IN (SELECT
t.sc_prod_service_id
FROM table3 t));
So I want to modify the query in such a way that if circuit_id form table2 is present in carriedBY_circuit or in CARRIED_CIRCUIT columns of table1. it should delete the row from table1.
You can try with merge:
merge into table1 t1
using (select t2.circuit_id from table2 t2 inner join table3 t3 on t2.circuit_name = t3.sc_prod_service_id) d
on (d.circuit_id = t1.carriedby_circuit or d.circuit_id = t1.carried_circuit)
when matched then delete;
Assuming you have 3 tables and you are working with ids. Table1, table2 and table3. Your best approach is to join table2 with table3. Then query its results, to delete from table1.
Example:
DELETE FROM table1
WHERE table1.id IN(SELECT distinct id FROM tabel1 UNION SELECT ID as id FROM tabel2);
PS: The union select will probably duplicate your Id´s, this is why I propose to use distinct.
Using the below query to copy records from one table to another, but i get error
insert into table1 (datestamp)
select datestamp
from table2
where table1.datestamp is null
I want to copy records of datestamp from table 2 to table 1 where datestamp in table 1 is null.
Is this what you mean?
insert into table1 (datestamp)
select datestamp
from table2
where table2.datestamp is null
You are referencing table1 datestamp in the where clause and this is not allowed.
Perhaps you really want an update. If so, you need a way to link the two tables:
update t1
set datestamp = t2.datestamp
from table1 t1 join
table2 t2
on t1.id = t2.id
where t1.datestamp is null
I'm assuming the tables are tied together by some unique id? We'll call that tableID.
UPDATE table1 t1, table2 t2
SET t1.datestamp = t2.datestamp
WHERE t1.datestamp IS NULL
AND t1.tableID = t2.tableID
Table1
...
LogEntryID *PrimaryKey*
Value
ThresholdID - - - Link to the appropriate threshold being applied to this log entry.
...
Table2
...
ThresholdID *PrimaryKey*
Threshold
...
All fields are integers.
The "..." thingies are there to show that these tables hold a lot more imformation than just this. They are set up this way for a reason, and I can't change it at this point.
I need write a SQL statement to select every record from Table1 where the Value field in that particular log record is less than the Threshold field in the linked record of Table2.
I'm newish to SQL, so I know this is a basic question.
If anyone can show me how this SQL statement would be structured, it would be greatly appreciated.
SELECT T1.*
FROM Table1 T1
JOIN Table2 T2 ON T2.ThresholdID = T1.ThresholdID
WHERE T2.Threshold > T1.Value
SELECT t1.*
FROM dbo.Table1 t1 INNER JOIN dbo.Table2 t2 ON t1.ThresholdID = t2.ThresholdID
WHERE t2.Threshold > t1.Value
SELECT * from table1 t1 join table2 t2 on (t1.thresholdId = t2.thresholdId)
where t1.value < t2.threshold;
SELECT t1.LogEntryID, t1.Value, t1.ThresholdID
FROM Table1 t1
INNER JOIN Table2 t2 ON t1.ThresholdID = t2.ThresholdID
WHERE t1.Value < t2.threshold
SELECT * FROM Table1
JOIN Table2
ON table1.ThresholdID = table2.ThresholdID --(assuming table 2 holds the same value to link them together)
WHERE
value < thresholdvalue
A 'JOIN' connects 2 tables based on the 'ON' clause (which can be multipart, using 'AND' and 'OR')
If you have 3 entries in table 2 which share table1's primary key (a one-to-many association) you will receive 3 rows in your result set.
for the tables below, for example:
Table 1:
Key Value
1 Hi
2 Bye
Table 2:
Table1Key 2nd_word
1 You
1 fellow
1 friend
2 now
this query:
SELECT * FROM Table1
JOIN Table2
on table1.key = table2.table1key
gets this result set:
Key Value Table1Key 2nd_word
1 Hi 1 You
1 Hi 1 fellow
1 Hi 1 friend
2 Bye 2 now
Note that JOIN will only return results when there is a match in the 2nd table, it will not return a result if there is no match. You can LEFT JOIN for that (all fields from the second table will be NULL).
JOINs can also be strung together, the result from the previous JOIN is used in place of the original table.