I need to get a row of information with max timestamp in postgresql. Below is a demo for this question:
drop table Mytable cascade
create table MyTable (usr char(1), event_dt timestamp without time zone);
insert into mytable values ('A','01-JAN-2009 11:10:11');
insert into mytable values ('A','02-JAN-2009 11:10:22');
insert into mytable values ('B','02-JAN-2009 01:01:59' );
insert into mytable values ('C', '31-DEC-2008 02:02:02');
insert into mytable values ('D', '31-DEC-2008 03:03:03');
If I do
select max(event_dt) from (
select usr,event_dt from mytable where usr= 'A') as foo
It is sort of what I need but it only returns the event_dt
"2009-01-02 11:10:22"
Where I want the usr as well sa event_dt from that row. How do I do it?
I would simply go for...
SELECT usr, event_dt FROM mytable ORDER BY event_dt DESC LIMIT 1
Related
I have two temp_tables defined as:
with temp_table_1 as (
select id from table_A where fname="john" limit 1
),
with temp_table_2 as (
select id from table_B where lname="smith" limit 1
)
These tables returns 1 row with just the id. I want to Insert a row into table_C where the column col_1 is equal to the result of temp_table_1 and the column col_2 is equal to the result of temp_table_2, and the third column (created_at) set to now:
The following fails for me:
insert into table_c (col_1, col_2, created_at)
values (temp_table_1.id, temp_table_2.id, current_timestamp at time zone 'UTC');
BEGIN;
CREATE temp TABLE table_a (
id bigint,
fname text
);
CREATE temp TABLE table_b (
id bigint,
lname text
);
CREATE temp TABLE table_c (
col_1 bigint,
col_2 bigint,
created_at timestamp
);
INSERT INTO table_a
VALUES (1, 'john');
INSERT INTO table_a
VALUES (1, 'john');
INSERT INTO table_b
VALUES (2, 'smith');
INSERT INTO table_b
VALUES (2, 'smith');
COMMIT;
WITH temp_table_1 AS (
SELECT
a.id AS a_id,
b.id AS b_id
FROM
table_a a,
table_b b
WHERE
a.fname = 'john'
AND b.lname = 'smith'
LIMIT 1)
INSERT INTO table_c (col_1, col_2, created_at)
SELECT
temp_table_1.a_id,
temp_table_1.b_id,
CURRENT_TIMESTAMP at time zone 'UTC'
FROM
temp_table_1
RETURNING
*;
That should be fairly straightforward with a cross join:
WITH temp_table_1 AS (... LIMIT 1),
WITH temp_table_2 AS (... LIMIT 1)
INSERT INTO table_c (col_1, col_2, created_at)
SELECT temp_table_1.id,
temp_table_2.id,
current_timestamp AT TIME ZONE 'UTC'
FROM temp_table_1 CROSS JOIN temp_table_2;
CREATE TABLE `testskm`(
`mem_id` NUMBER(5) NOT NULL,
`mem_sal` NUMBER(5) NOT NULL);
insert into `testskm` values (1,100);
insert into `testskm` values (1,200);
insert into `testskm` values (2,350);
insert into testskm values (2,150);
insert into testskm values (3,12);
insert into testskm values (1,300);
insert into testskm values (2,50);
insert into testskm values (3,13);
insert into testskm values (3,14);
insert into testskm values (3,15);
i have insert statements for mem_id 1,2, & 3. I want to get the last 2 inserted records in the table for all mem_id.
I have the tried the below code , but its giving me only records based on the mem_sal as i used the order by..
select * from(
select
mem_id, mem_sal,
--max(sysdate) over (partition by mem_id) latest,
rank() over( partition BY mem_id order by mem_sal ) RISK_ORDER
from testskm)
where RISK_ORDER <= 2
i want output of these inserted records:
insert into `testskm` values (1,200);
insert into `testskm` values (1,300);
insert into `testskm` values (2,150);
insert into `testskm` values (2,50);
insert into `testskm` values (3,14);
insert into `testskm` values (3,15);
SQL tables represent unordered sets. There is no "last two rows" unless a column specifies the ordering. Your table has no such column.
You can define one. In MySQL, this looks like:
create table `testskm` (
testskm_id int auto_increment primary key,
`mem_id` int NOT NULL,
`mem_sal` int NOT NULL
);
Then you can use row_number():
select ts.*
from (select ts.*, row_number() over (partition by mem_id order by testskm_id desc) as seqnum
from testskm ts
) ts
where seqnum <= 2;
Here is a db<>fiddle.
I need to build a SQL query that must be able to insert data in a first table, grab the inserted ID and then use it as foreign key in the following tables.
WITH inserted AS (
INSERT INTO firstTable (name) VALUES ('somename') RETURNING id
)
SELECT * FROM inserted; -- this has the inserted id
INSERT INTO secondTable (name, foreign_id) VALUES ('someexternalname', ???)
So how do I reference the id in inserted in the secondTable insert?
You have completed this 80% percent, the complete SQL is:
with inserted as (
insert into first_table(name) values ('somename') returning id
)
insert into second_table(name, foreign_id) select 'someexternalname',id from inserted
You can do this:
WITH inserted AS (
INSERT INTO firstTable (name) VALUES ('somename') RETURNING id
)
INSERT INTO secondTable (name, foreign_id)
SELECT
'someexternalname',
id
FROM inserted;
You can try this:
INSERT INTO secondTable (name, foreign_id) VALUES ('someexternalname', (SELECT
MAX (id) FROM firstTable))
Table1
Id bigint primary key identity(1,1)
Status nvarchar(20)
Insert dummy data
Insert into Table1 values ('Open') --1
Insert into Table1 values ('Open') --2
Insert into Table1 values ('Grabbed') --3
Insert into Table1 values ('Closed') --4
Insert into Table1 values ('Closed') --5
Insert into Table1 values ('Open') --6
How would I construct a single select statement which orders the data where records with 'Grabbed' status is first, followed by 'Closed', followed by 'Open' in SQL Server
Output:
Id Status
3 Grabbed
4 Closed
5 Closed
1 Open
2 Open
6 Open
I think you need something like this:
select *
from yourTable
order by case when Status = 'Grabbed' then 1
when Status = 'Closed' then 2
when Status = 'Open' then 3
else 4 end
, Id;
[SQL Fiddle Demo]
Another way is to using CTE like this:
;with cte as (
select 'Grabbed' [Status], 1 [order]
union all select 'Closed', 2
union all select 'Open', 3
)
select t.*
from yourTable t
left join cte
on t.[Status] = cte.[Status]
order by cte.[order], Id;
[SQL Fiddle Demo]
This could be done much better with a properly normalized design:
Do not store your Status as a textual content. Just imagine a typo (a row with Grabed)...
Further more a lookup table allows you to add side data, e.g. a sort order.
CREATE TABLE StatusLookUp(StatusID INT IDENTITY PRIMARY KEY /*you should name your constraints!*/
,StatusName VARCHAR(100) NOT NULL
,SortRank INT NOT NULL)
INSERT INTO StatusLookUp VALUES
('Open',99) --ID=1
,('Closed',50)--ID=2
,('Grabbed',10)--ID=3
CREATE TABLE Table1(Id bigint primary key identity(1,1) /*you should name your constraints!*/
,StatusID INT FOREIGN KEY REFERENCES StatusLookUp(StatusID));
Insert into Table1 values (1) --1
Insert into Table1 values (1) --2
Insert into Table1 values (3) --3
Insert into Table1 values (2) --4
Insert into Table1 values (2) --5
Insert into Table1 values (1) --6
SELECT *
FROM Table1 AS t1
INNER JOIN StatusLookUp AS s ON t1.StatusID=s.StatusID
ORDER BY s.SortRank;
I find that the simplest method uses a string:
order by charindex(status, 'Grabbed,Closed,Open')
or:
order by charindex(',' + status + ',', ',Grabbed,Closed,Open,')
If you are going to put values in the query, I think the easiest way uses values():
select t1.*
from t1 left join
(values ('Grabbed', 1), ('Closed', 2), ('Open', 3)) v(status, priority)
on t1.status = v.status
order by coalesce(v.priority, 4);
Finally. This need suggests that you should have a reference table for statuses. Rather than putting the string name in other tables, put an id. The reference table can have the priority as well as other information.
Try this:
select Id,status from tablename where status='Grabbed'
union
select Id,status from tablename where status='Closed'
union
select Id,status from tablename where status='Open'
I found an old table without a primary key, and in order to add one, I have to add a new column and fill it with sequence values. I have another column which contains the time of when the record was created, so I want to insert the sequence values to the table sorted by the column with the time.
I'm not sure how to do it. I tried using PL\SQL - I created a cursor for a query that returns the table with an ORDER BY, and then update for each record the cursor returns but it didn't work.
Is there a smart working way to do this?
Thanks in advance.
Another option is just to use a correlated subquery, with the wrinkle of a nested subquery to generate the row number. Setting up some sample data:
create table t42 (datefield date);
insert into t42 (datefield) values (sysdate - 7);
insert into t42 (datefield) values (sysdate + 6);
insert into t42 (datefield) values (sysdate - 5);
insert into t42 (datefield) values (sysdate + 4);
insert into t42 (datefield) values (sysdate - 3);
insert into t42 (datefield) values (sysdate + 2);
select * from t42;
DATEFIELD
---------
12-JUL-12
25-JUL-12
14-JUL-12
23-JUL-12
16-JUL-12
21-JUL-12
Then adding and populating the new column:
alter table t42 add (id number);
update t42 t1 set t1.id = (
select rn from (
select rowid, row_number() over (order by datefield) as rn
from t42
) t2
where t2.rowid = t1.rowid
);
select * from t42 order by id;
DATEFIELD ID
--------- ----------
12-JUL-12 1
14-JUL-12 2
16-JUL-12 3
21-JUL-12 4
23-JUL-12 5
25-JUL-12 6
Since this is a synthetic key, making it match the order of another column seems a bit pointless, but I guess doesn't do any harm.
To complete the task:
alter table t42 modify id not null;
alter table t42 add constraint t42_pk primary key (id);
First of all, create new field and allow null values.
Then, update field from other table or query. Best approach is to use merge statement.
Here a sample from documentation:
MERGE INTO bonuses D
USING (SELECT employee_id, salary, department_id FROM employees
WHERE department_id = 80) S
ON (D.employee_id = S.employee_id)
WHEN MATCHED THEN UPDATE SET D.bonus = D.bonus + S.salary*.01
DELETE WHERE (S.salary > 8000)
WHEN NOT MATCHED THEN INSERT (D.employee_id, D.bonus)
VALUES (S.employee_id, S.salary*.01)
WHERE (S.salary <= 8000);
Finally, set as non null this new field and promote it to primary key.
Here sample sentences:
ALTER TABLE
customer
MODIFY
(
your_new_field varchar2(100) not null
)
;
ALTER TABLE
customer
ADD CONSTRAINT customer_pk PRIMARY KEY (your_new_field)
;
One simple way is to create a new table, with new column an all other columns:
create table newt (
newtID int primary key not null,
. . .
)
Then insert all the old data into it:
insert into newt
select row_number() over (order by <CreatedAt>), t.*
from t
(You can substitute all the columns in, instead of using "*". Having the columns by name is the better practice. This is shorter, plus, I don't know the column names.)
If you alter the table to add the column, then the column will appear at the end. I find that quite awkward for the primary key. If you do that, though, you can update it as:
with t as (select row_number() over (order by <CreatedAt>) as seqnum, t.*
from t
)
update t
set newtID = seqnum