I have a log table like this:
fill_logs(
log_id number,
text varchar2(1000),
executed_on date,
...
)
It saves a log of some operations. And when I query this table I want this query to be sorted in descending order of the executed_on column by default. Sounds stupid, but I don't want to write order by clause every time.
So create a view SELECT * FROM FILL_LOGS ORDER BY EXECUTED_ON and use that view instead of the table.
Related
So my use case is i have to find the location of the primary key column so that i can write query like select * from my_table where ID <='00000536-37ee-471c-a8e0-3d233b8102f5'
So my table has a primary key which is varchar type and values of the column is GUID generated by an application.
Here is an example of primary key
000000bd-104e-4fd6-a791-c5422f29e1b5
0000016e-7e68-4453-b360-7ffd1627dc22
00000196-2dba-4532-8cba-1e853c466697
0000025a-cfae-41b4-b8e7-ef854d49e54a
00000260-8bdb-4b30-acdb-5a67efd4dbfe
00000366-552d-48a0-b8a1-20190ccd087c
000003f2-d6d8-4a51-96cc-407063bc568b
000003ff-3d16-4e88-9cf3-bcdf01c39a2b
00000487-1e6c-4d6d-a683-6f11d517962c
000004cc-6359-4a9a-aa2a-70a6b73a06b1
00000536-37ee-471c-a8e0-3d233b8102f5
Now i need to use this table in aws DMS which accepts only query like select * from table where column =,<=,>=
My use case is to find the exact location of the millions of GUID so that i can divide table into multiple query and select based on GUID .
For example if we have 100th GID is 00000536-37ee-471c-a8e0-3d233b8102f5 then i can write query like select * from my table where GUID <=100
The limitation is i can not add any new columns in the existing table because application impact is huge .
How can i do this ?
One Option that i thought but wanted to confirm is below
Create a temp table
Temp table will have auto generated sequence and ID column
Inset into temp table select only GUID from main table with order of GUID .
In this case the value will be stored on order and i an first select GUID based on 100th number and then i can pass that GUID and write my oroginal query
But i am not sure whether this will work on not
Can some one suggest on this or suggest some other option ?
So let me explain what i want .
I want DMS to read may main table in parallel and migrate .
So lets say one DMS task can read nd migrate from 1 to 100,another 100 to 200 another >200 like that .
Currently i can not do because we dont know the position of the primary key and write the query .
If you want to divide your table into chunks of equal sizes, I would take advantage of the hexadecimal nature of the GUIDs. It will be 256 instead of 100 chunks, but this might be acceptable.
CREATE TABLE t (pk VARCHAR2(36) PRIMARY KEY);
INSERT INTO t VALUES ('000000bd-104e-4fd6-a791-c5422f29e1b5');
The easiest option would be
SELECT * FROM t WHERE pk LIKE '%b5';
A bit more advanced:
SELECT pk, to_number(substr(pk, -2),'xx') FROM t;
If you have millions of rows, this is probably faster:
ALTER TABLE t ADD (mycol GENERATED ALWAYS AS (to_number(substr(pk, -2),'xx')));
CREATE INDEX i ON t(mycol);
SELECT * FROM t WHERE mycol=181;
Once your migration is done, you can undo the additional virtual column:
DROP INDEX i;
ALTER TABLE t DROP (mycol);
Just want to know is this possible.
Say that if i have value 'X' and iam sure that this is referenced in some other tables as PK value but not sure about exactly which table is that, so i would like to know the list of those tables.
Pseudo query of above what i mentioned
SELECT TABLE_NAME FROM DBA_TABLES WHERE <<ATLEAST ONE OF THE TABLE ROW PK VALUE IS MATCHING EQUAL TO 'X'>>;
Using hive, I'm trying to concatenate columns from one table and insert them in another table using the query
insert into table temp_error
select * from (Select 'temp_test','abcd','abcd','abcd',
from_unixtime(unix_timestamp()),concat_ws('|',sno,name,age)
from temp_test_string)c;
I get the required output till I use Select *. But as soon as I try to insert it into the table, it does not give concatenated output but gives the value of sno only instead of whole concatenated output.
Thanks guys.
I found why it was behaving that way. It's because while creating table I gave "separate fields by '|'". So what I was trying to insert as a string into the table, hive was interpreting it as different columns.
I want to write a query such that it returns the table name (of the table I am querying) and some other values. Something like:
select table_name, col1, col2 from table_name;
I need to do this in Hive. Any idea how I can get the table name of the table I am querying?
Basically, I am creating a lookup table that stores the table name and some other information on a daily basis in Hive. Since Hive does not (at least the version we are using) support full-fledged INSERTs, I am trying to use the workaround where we can INSERT into a table with a SELECT query that queries another table. Part of this involves actually storing the table name as well. How can this be achieved?
For the purposes of my use case, this will suffice:
select 'table_name', col1, col2 from table_name;
It returns the table name with the other columns that I will require.
Hi I have a database with loads of columns and I want to insert couple of records for testing, now in order to insert something into that database I'd have to write large query .. is it possible to do something like this
INSERT INTO table (SELECT FROM table WHERE id='5') .. I try to insert the row with ID 5 but I think this will create a problem because it will try to duplicate a record, is it possible to change this ID 5 to let say 1000 then I'd be able to insert data without writing complex query and while doing so avoiding replication of data .. tnx
In PL/SQL you can do something like this:
declare
l_rec table%rowtype;
begin
select * into l_rec from table where id='5';
l_rec.id := 1000;
insert into table values l_rec;
end;
If you have a trigger on the table to handle the primary key from a sequence (:NEW.id = seq_sequence.NEXTVAL) then you should be able to do:
INSERT INTO table
(SELECT columns_needed FROM table WHERE whatever)
This will allow you to add in many rows at one (the number being limited by the WHERE clause). You'll need to select the columns that are required by the table to be not null or not having default values. Beware of any unique constraints as well.
Otherwise you'll be looking at PL/SQL or some other form of script to insert multiple rows.
For each column that has no default value or you want to insert the values other than default, you will need to provide the explicit name and value.
You only can use an implicit list (*) if you want to select all columns and insert them as they are.
Since you are changing the PRIMARY KEY, you need to enumerate.
However, you can create a before update trigger and change the value of the PRIMARY KEY in this trigger.
Note that the trigger cannot reference the table itself, so you will need to provide some other way to get the unique number (like a sequence):
CREATE TRIGGER trg_mytable_bi BEFORE INSERT ON mytable FOR EACH ROW
BEGIN
:NEW.id := s_mytable.nextval;
END;
This way you can use the asterisk but it will always replace the value of the PRIMARY KEY.