I have a table with several employees. They have the following columns empid,datecolumn1,is_valid.
Very few employees have a more than one record in the table. If an employee has more than one record in the table I would like to 'invalidate' one of the records on the following condition:
1. If a employee has more than one record in the table then the record with no value in the datecolumn1 is valid (update is_valid to 1) and the record with value in datecolumn1 is not valid (update is_valid to 0).
How do I accomplish this?
As Ben points out, you've stated that if datecolumn1 is NULL you want the is_valid column to be set to both 0 and 1. Assuming you fix that, you may need to adjust this CASE statement depending on which way you decide is correct.
UPDATE employees
SET is_valid = (CASE WHEN datecolumn1 IS NULL
THEN 1
ELSE 0
END)
WHERE empid IN (SELECT e.empid
FROM employees e
GROUP BY emempid
HAVING COUNT(*) > 1)
create a staging table, and fill it by a SELECT on the original table with a GROUP BY employee Id (or whatever your unique identifier is). Create a second staging table and fill it by SELECTING on the original table and excluding all rows that match rows in your grouped table. Now you have a table that contains only those people with multiple rows. From your original table, set is_valid to 0 on all rows that match employee id with the second staging table and also have no datecolumn1 (or perhaps that also have a datecolumn1 - your question as of this writing is a bit unclear.) and is_valid to 1 on the others. Once done with that, delete the staging tables, and you should have what you need.
You could also do this with a single more complicated multiselect call, but I find it helpful to use staging tables when things get complicated.
Related
I created three tables A (id, name, date, realnumber, integer), B (id, name, date, realnumber, integer), and C which is identical to table A. It only has two more columns called integerB and sequence s. I want to create a trigger which would fire after insert on table B for each row input so that it saves the referenced row of Table A and adds integer from input row of table B in column integerB of table C. If the row already exists in Table C only integerB should be added. When it comes to sequence s, next value is added with first insert of row of table A.
Simple explanation: Table C is a copy of table A with two additional columns: integerB and sequence. The point of the trigger is to add new rows from table A without repetition, integerB from table B(integer in table B) and sequence should start with 1 and increment by 1. If the row in table A is repeated then only integerB should be updated.
I did not work with triggers that much, so I am not sure how to solve the problem when I have to insert data from multiple tables. Here is my trigger.
CREATE OR REPLACE TRIGGER trig1
AFTER INSERT ON B
FOR EACH ROW
INSERT INTO C (integerB) VALUES (NEW.integer);
INSERT INTO C (id, name, date, realnumber)
SELECT a.id, a.name, a.date, a.realnumber FROM A a;
END;
/
First off you really need to use better column and table names as a lot of these are reserved words... This makes everything far more complicated than it needs to be.
It isn't entirely clear what you want to do but it seems that if someone was to insert a record with ID = 1 into B then you want to get the values from A for ID = 1 and store them in C along with the integer value inserted into B
In which case you want to use an MERGE statement (UPSERT) in your trigger and something like
CREATE OR REPLACE TRIGGER T1
AFTER INSERT ON B
FOR EACH ROW
BEGIN
MERGE INTO C C
USING (SELECT * FROM A WHERE ID = :NEW.ID) A
ON (C.ID = :NEW.ID)
WHEN MATCHED THEN UPDATE
SET C.INTEGERB = :NEW.INTEGER,
C.SEQUENCE = C.SEQUENCE + 1
WHEN NOT MATCHED THEN
INSERT (ID, NAME, DATE, REALNUMBER, INTEGER, INTEGERB, SEQUENCE)
VALUES (A.ID, A.NAME. A.DATE, A.REALNUMBER, A.INTEGER, :NEW.INTEGER, 0);
END;
/
For sequence this has been set to 0 when a new record is inserted into C and then incremented each time integerB is updated. I am not sure if this is waht you want or not.
You should be able to tweak this to match the exact joins and logic you need.
Tip
Get your SQL statement working with literal values first and then translate it into your trigger. It will be much easier if you can get something working manually first before you attempt to make things more complicated
There's total of three tables involved. one header base table, one material
base table, one staging table.
I have created the staging table with 4 columns, the values will be
updated from csv uploaded, column 1 is batch_no, column 2 is for
attribute.
>header base table(h) has batch_no and batch_id
>material base table(m) has batch_id, attr_m (empty, to be updated)
>staging table(s) has batch_no and attr_s
create table he (BATCH_ID number, BATCH_NO varchar2(30));
create table me (a6 varchar2(30), BATCH_id number);
create table s (batch_no varchar2(30), att varchar2(30));
I want to take values from attr_s and update attr_m against batch_no. How do I do that?
Here's my code, please help me fix this code, it doesn't work
update me
set a6 = (select att
from s where batch_no = (select he.batch_no
from he, s
where he.batch_no=s.batch_no))
error received:
single row subquery return multiple rows.
single row subquery return multiple rows
The update statement is applied to each individual row in ME. Therefore the assignment operation requires one scalar value to be returned from the subquery. Your subquery is returning multiple values, hence the error.
To fix this you need to further restrict the subquery so it returns one row for each row in ME. From your data model the only way to do this is with the BATCH_ID, like so:
update me
set a6 = (select att
from s where batch_no = (select he.batch_no
from he, s
where he.batch_no=s.batch_no
and he.batch_id = me.batch_id))
Such a solution will work providing that there is only one record in S which matches a given permutation of (batch_no, batch_id). As you have provided any sample data I can't verify that the above statement will actually solve your problem.
I am trying to replace all of the NULL values to 0 in a column of a big table in HIVE.
However, every time I try to implement some code I end up generating a new column to the table. The column I am trying to change/modify still exists and still has the NULL values but the new column that is automatically generated (i.e. _c1) is what I want the column I am trying to modify, to look like.
I tried to run a COALESCE but that also ended up generating a new column. I also tried to implement a CASE WHEN, but the same results ensued.
Select *,
CASE WHEN columnname IS NULL THEN 0
ELSE columnname
END
from tablename;
Also tried
SELECT coalesce(columnname, CAST(0 AS BIGINT)) FROM tablename
I would just like to update the table with the other columns being as is but the column I want to modify still has its original name but instead of NULL values it has 0's that replaced them.
I don't want to generate a new column but modify an existing one.
How should I do that?
Use insert overwrite .. option.
insert overwrite table tablename
select c1,c2,...,coalesce(columnname,0) as columnname
from tablename
Note that you have to specify all the other column names required in select.
I have a source table, and a history table. They are identical, except the history table has a notes column as the last column.
The table is large, 55 columns, which I do not want to list all the columns. We do not want to use a trigger on this, but just create the history entry in the code itself.
If I simply do an INSERT INTO <history> SELECT * FROM <source> WHERE...... I will get "not enough values".
I'm hoping to do something of this nature: (Note this is just an anonymous block)
DECLARE
v_old_rec company_table%ROWTYPE;
BEGIN
SELECT * INTO v_old_rec
FROM company_table
WHERE company_id = 32789;
INSERT INTO company_table_hist
VALUES v_old_rec || ',MONTHLY UPDATE';
END;
Anything like this possible, so I do not have to list 55 columns?
Thank you.
It's quite simple actually:
INSERT INTO company_table_hist
(SELECT t.*, MONTHLY_UPD
FROM company_table t
WHERE company_id = 32789);
Of course monthly_upd must be bound somehow
Table 1:
Name, x1-X2, fk1, fk2.
Table 2:
K1(parent for table 1),X
How to update table 1 whose second column x1-x2 depands on fk1,fk2 from Table 2
Table1:
a,1.0,1,2
b,-3.0,2,3
Table 2
1,4.0
2,5.0
3,2.0
With this setup:
CREATE TABLE table2 (k NUMBER PRIMARY KEY, x NUMBER);
CREATE TABLE table1 (
NAME VARCHAR2(10) PRIMARY KEY,
diff NUMBER,
fk1 NUMBER REFERENCES table2,
fk2 NUMBER REFERENCES table2);
the following update will "refresh" the colum table1.diff with the values of table2:
SQL> UPDATE (SELECT child.diff old_diff, parent2.x - parent1.x new_diff
2 FROM table1 child
3 JOIN table2 parent1 ON (child.fk1 = parent1.k)
4 JOIN table2 parent2 ON (child.fk2 = parent2.k))
5 SET old_diff = new_diff
6 WHERE old_diff != new_diff
7 OR (old_diff IS NULL AND new_diff IS NOT NULL)
8 OR (old_diff IS NOT NULL AND new_diff IS NULL);
Only the rows that need updating will be refreshed (thanks to the where clause).
Not quite sure I understand the question, referential integrity constraints do not prevent you from updating a table. If you need to do a lot of work in a transaction you can look into Deferred Constraints. Is there any chance you could clarify what you mean?
Not sure exactly what the problem is, maybe you need to rephrase the question a little.
In general, the foreign key constraint makes sure that there exists a corresponding row in the referenced table.
When you update a row with a foreign key, and try to set a value that does not point to such a master row, you will get an error, either immediately or when you commit (depending on when the constraint is enforced, it can be deferred).
Other than that, the update is no different than any other update.
Since the data in table 1 is dependent on the data in table 2 you won't be able to "Update" table 1 directly.
You will have to perform the update on table 2 and then recalculate table 1.
You could do it inside a transaction or perhaps a trigger on table 2.
Another option may be to have table one only hold the foreign keys and the name and then create a view that calculates the X1-X2 value.
EDIT
After looking at the sample data, I don't think you can unambiguously have table 2 be updates as a result of an update on table 1.
For example if you update the second column of table 1 to be 43, how would you know what values to set the specific rows of table 2 (it could be 40 and 3, 20 and 23, etc.)