I have two different table:
Table1, Table2.
Two tables have different columns and nothing in common. What I am looking to get is
if Table1 is empty/null then
output Table2
else
output table1
Is it possible to get it done in Oracle? Any leads would be appreciated.
Accordingly to your phrase:
if Table1 is empty/null then output Table2 else output table1
I think the solution is (I briefed Table1, Table2 by A, B respectively ):
--I created this tables to test the solution
create table A( id number, val varchar2(5));
create table B( code varchar2(5), event_dt date);
insert into b(code, event_dt)
values ('test', sysdate);
--query(1)
select b.code, to_char(b.event_dt,'yyyy-mm-dd')
from b
where not exists (select 1 from a)
union
select to_char(id), to_char(val)
from a
;
--now insert data on the other table (to test purposes)
insert into A(id, val)
values(1, 'TestA');
--run the query(1) again
The key is "union", kind of repeat your query when the first portion deals to no data
found.
Please remember to CAST your columns to achieve the same DATA-TYPES required by UNION
Best regards.
I have a need to do the following
UPDATE TABLE2 t2
SET t2.product_id = (select t1.product_id from
table1 t1 where t1.matching_id = t2.matching_id)
Except that TABLE2 has 27 million records. The product_id is a newly added column and hence populating data to it.
I could use a cursor , break down my record set in TABLE2 to a reasonably smaller number, But with 27 million records, I am not sure whats the best way.
Pl suggest, even if it means exporting my data to excel.
Update - THe matching columns are indexed too.
The only thing I could do different is replace the update for a CREATE TABLE AS
CREATE TABLE table2_new AS
SELECT t2.* (less product_id), t1.product_id
FROM table1 t1
JOIN table2 t2
ON t1.matching_id = t2.matching_id
But later you will have to add the CONSTRAINTS manually, delete table2 and replace for table2_new
update (select t1.product_id as old_product_id, t2.product_id as new_product_id
from table1 t1
join table2 t2 on (t1.matching_id = t2.matching_id)) t
set t.new_product_id = t.old_product_id
I want to write a query which finds the difference between two tables and writes updates or new data into third table. My two tables have identical column names. Third table which captures changes have extra column called comment. I would like to insert the comment whether it is a new row or updated row based on the row modification.
**TABLE1 (BACKUP)**
KEY,FIRST_NAME,LAST_NAME,CITY
1,RAM,KUMAR,INDIA
2,TOM,MOODY,ENGLAND
3,MOHAMMAD,HAFEEZ,PAKISTAN
4,MONIKA,SAM,USA
5,MIKE,PALEDINO,USA
**TABLE2 (CURRENT)**
KEY,FIRST_NAME,LAST_NAME,CITY
1,RAM,KUMAR,USA
2,TOM,MOODY,ENGLAND
3,MOHAMMAD,HAFEEZ,PAKISTAN
4,MONIKA,SAM,INDIA
5,MIKE,PALEDINO,USA
6,MAHELA,JAYA,SL
**TABLE3 (DIFFERENCE FROM TABLE2 TO TABLE1)**
KEY,FIRST_NAME,LAST_NAME,CITY,COMMENT
1,RAM,KUMAR,USA,UPDATE
4,MONIKA,SAM,INDIA,UPDATE
6,MAHELA,JAYA,SL,INSERT
table scripts
DROP TABLE TABLE1;
DROP TABLE TABLE2;
DROP TABLE TABLE3;
CREATE TABLE TABLE1
(
KEY NUMBER,
FIRST_NAME VARCHAR2(100),
LAST_NAME VARCHAR2(100),
CITY VARCHAR2(50)
);
/
CREATE TABLE TABLE2
(
KEY NUMBER,
FIRST_NAME VARCHAR2(100),
LAST_NAME VARCHAR2(100),
CITY VARCHAR2(50)
);
/
CREATE TABLE TABLE3
(
KEY NUMBER,
FIRST_NAME VARCHAR2(100),
LAST_NAME VARCHAR2(100),
CITY VARCHAR2(50),
COMMENTS VARCHAR2(200)
);
/
INSERT ALL
INTO TABLE1
VALUES(1,'RAM','KUMAR','INDIA')
INTO TABLE1 VALUES(2,'TOM','MOODY','ENGLAND')
INTO TABLE1 VALUES(3,'MOHAMMAD','HAFEEZ','PAKISTAN')
INTO TABLE1 VALUES(4,'MONIKA','SAM','USA')
INTO TABLE1 VALUES(5,'MIKE','PALEDINO','USA')
SELECT 1 FROM DUAL;
/
INSERT ALL
INTO TABLE2
VALUES(1,'RAM','KUMAR','USA')
INTO TABLE2 VALUES(2,'TOM','MOODY','ENGLAND')
INTO TABLE2 VALUES(3,'MOHAMMAD','HAFEEZ','PAKISTAN')
INTO TABLE2 VALUES(4,'MONIKA','SAM','INDIA')
INTO TABLE2 VALUES(5,'MIKE','PALEDINO','USA')
INTO TABLE2 VALUES(6,'MAHELA','JAYA','SL')
SELECT 1 FROM DUAL;
I was using the merge statement to accomplish the same. but i have hit a roadblock in merge statement , it's rhrowing an error "SQL Error: ORA-00905: missing keyword
00905. 00000 - "missing keyword"" I dont understand where is the error. please help
INSERT INTO TABLE3
SELECT KEY,FIRST_NAME,LAST_NAME,CITY,NULL AS COMMENTS FROM TABLE2
MINUS
SELECT KEY,FIRST_NAME,LAST_NAME,CITY,NULL AS COMMENTS FROM TABLE1
;
MERGE INTO TABLE3 A
USING TABLE1 B
ON (A.KEY=B.KEY)
WHEN MATCHED THEN
UPDATE SET A.COMMENTS='UPDATED'
WHEN NOT MATCHED THEN
UPDATE SET A.COMMENTS='INSERTED';
There is no such WHEN NOT MATCHED THEN UPDATE clause, you should use WHEN NOT MATCHED THEN INSERT. Refer to MERGE for details.
A few assumptions made about the data:
An INSERT event will be a record identified by its key in table2 (current data) that does not have a matching key in the original back-up table: table1.
An UPDATE event is a field that exists in both table1 and table2 for the same KEY but is not the same.
Records which did not change between tables are not to be recorded in table3.
Example Query: Check for Updates
SELECT UPD_QUERY.NEW_CITY, 'UPDATED' as COMMENTS
FROM (SELECT CASE WHEN REPLACE(CURR.CITY, BKUP.CITY,'') IS NOT NULL THEN CURR.CITY
ELSE NULL END as NEW_CITY
FROM table1 BKUP, table2 CURR
WHERE BKUP.KEY = CURR.KEY) UPD_QUERY
WHERE UPD_QUERY.NEW_CITY is NOT NULL;
You can repeat this comparison method for the other fields:
SELECT UPD_QUERY.*
FROM (SELECT CURR.KEY,
CASE WHEN REPLACE(CURR.FIRST_NAME, BKUP.FIRST_NAME,'') IS NOT NULL
THEN CURR.FIRST_NAME
ELSE NULL END as FIRST_NAME,
CASE WHEN REPLACE(CURR.LAST_NAME, BKUP.LAST_NAME,'') IS NOT NULL
THEN CURR.LAST_NAME
ELSE NULL END as LAST_NAME,
CASE WHEN REPLACE(CURR.CITY, BKUP.CITY,'') IS NOT NULL
THEN CURR.CITY
ELSE NULL END as CITY
FROM table1 BKUP, table2 CURR
WHERE BKUP.KEY = CURR.KEY) UPD_QUERY
WHERE COALESCE(UPD_QUERY.FIRST_NAME, UPD_QUERY.LAST_NAME, UPD_QUERY.CITY)
is NOT NULL;
NOTE: This could get unwieldy very quickly if the number of columns compared are many. Since the target table design (table3) requires not only identification of a change, but the field and its new value are also recorded.
Example Query: Look for Newly Added Records
SELECT CURR.*, 'INSERTED' as COMMENTS
FROM table2 CURR, table1 BKUP
WHERE CURR.KEY = BKUP.KEY(+)
AND BKUP.KEY is NULL;
Basically MERGE forces the operation: MATCHED=UPDATE (or DELETE), NOT MATCHED = INSERT. It's in the docs.
You can do what you want but you need two insert statements with different set operators,
For UPDATED:
Insert into table3
table1 INTERSECT table2
For INSERTED:
Insert into table3
table2 MINUS table1
update tablename set (col1,col2,col3) = (select col1,col2,col3 from tableName2 order by tablenmae2.col4) return error
Missing ). The query works fine if I remove the order by clause
ORDER BY is not allowed in a subquery within an UPDATE. So you get the error "Missing )" because the parser expects the subquery to end at the point that you have ORDER BY.
What is the ORDER BY intended to do?
What you probably have in mind is something like:
UPDATE TableName
SET (Col1, Col2, Col3) = (SELECT T2.Col1, T2.Col2, T2.Col3
FROM TableName2 AS T2
WHERE TableName.Col4 = T2.Col4
)
WHERE EXISTS(SELECT * FROM TableName2 AS T2 WHERE TableName.Col4 = T2.Col4);
This clumsy looking operation:
Grabs rows from TableName2 that match TableName on the value in Col4 and updates TableName with the values from the corresponding columns.
Ensures that only rows in TableName with a corresponding row in TableName2 are altered; if you drop the WHERE clause from the UPDATE, you replace the values in Col1, Col2, and Col3 with nulls if there are rows in TableName without a matching entry in TableName2.
Some DBMS also support an update-join notation to reduce the ghastliness of this notation.
I have 2 tables - A and B . Table A has two columns, pkey (primary key) and col1. Table B also has two columns, pr_key (primary key but not a foreign key) and column1. Both tables have 4 rows. Table B has no values in column1, while table A has column1 values for all 4 rows. So my data looks like this
Table A
pkey col1
A 10
B 20
C 30
D 40
Table B
pr_key column1
A null
B null
C null
D null
I want to update table B to set the column1 value of each row equal to the column1 value of the equivalent row from table A in a single DML statement.
Should be something like that (depends on SQL implementation you use, but in general, the following is rather standard. In particular should work in MS-SQL and in MySQL.
INSERT INTO tblB (pr_key, column1)
SELECT pkey, col1
FROM tblA
-- WHERE some condition (if you don't want 100% of A to be copied)
The question is a bit unclear as to the nature of tblB's pr_key, if for some reason this was a default/auto-incremented key for that table, it could just then be omitted from both the column list (in parenthesis) and in the SELECT that follows. In this fashion upon insertion of each new row, a new value would be generated.
Edit: It appears the OP actually wants to update table B with values from A.
The syntax for this should then be something like
UPDATE tblB
SET Column1 = A.Col1
FROM tblA AS A
JOIN tblB AS B ON B.pr_key = A.pkey
This may perform better:
MERGE INTO tableB
USING (select pkey, col1 from tableA) a
ON (tableB.pr_key = a.pkey)
WHEN MATCHED THEN UPDATE
SET tableB.column1 = a.col1;
It sounds like you want to do a correlated update. The syntax for that in Oracle is
UPDATE tableB b
SET column1 = (SELECT a.column1
FROM tableA a
WHERE a.pkey = b.pr_key)
WHERE EXISTS( SELECT 1
FROM tableA a
WHERE a.pkey = b.pr_key )
The WHERE EXISTS clause isn't necessary if tableA and tableB each have 4 rows and have the same set of keys in each. It is much safer to include that option, though, to avoid updating column1 values of tableB to NULL if there is no matching row in tableA.