Updating a table in oracle

Posted by / 30-May-2018 02:48

Updating a table in oracle

You will be given questions that you need to solve.

After each exercise, we provide the solution so you can check your answer.

UPDATE Table1 T1 SET T1= (SELECT T2FROM Table2 T2 WHERE T2= T1.id), T1= (SELECT T2FROM Table2 T2 WHERE T2= T1.id) WHERE T1IN (SELECT T2FROM Table2 T2 WHERE T2= T1.id); The full example is here: beef is in having the columns that you want to use as the key in parentheses in the where clause before 'in' and have the select statement with the same column names in parentheses.

where (column1,column2) in ( I didn't down rate, but it isn't a good solution.

UPDATE summary_data SET current_category = (SELECT category_id FROM products WHERE products.product_id = summary_data.product_id) WHERE EXISTS (SELECT category_id FROM products WHERE products.product_id = summary_data.product_id); If you want to test your skills using the SQL UPDATE statement, try some of our practice exercises.

These exercises allow you to try out your skills with the UPDATE statement.

I have one table A has column (id, field_1,field_2), and another table B has column (id,field_2) Now I want to merge table B to A, that means i want to update field_2 in table A to value of table B. BTW I am using oracle Thanks Now, each time the above is executed, it will do it across all rows in the table.

If this is something you need to do all the time, I would suggest something else, but for a one-off or very small tables it should be sufficient.

You could create a trigger on table B that updates table A every time field_2 on table B is updated.The trick is that when you do select * from a pair of tables with duplicate column names, the 2nd one will get named _1.So here's what I came up with: Thank you for your interest in this question. This means that you have to select on all the fields which comprise a unique key -- a non-unique primary key is not sufficient.Without uniqueness, you are reduced to something like @Paul Karr's loop -- and if there is not a unique correlation, then more than one target row may be updated for each source row.

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It is best to use the above update of a JOIN if possible (optimizer has best chance of getting a good plan). REGISTRATION where not exists (select null from VIStemp. b)in privious question i told u that i am exporting incremental and edited data by using system date. In my B(big table record-79186) and in S(small table record-12871). Can you please tell me which option performs better if the number of records are in millions. I have a table t1 which is having all orders information.

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