Updating two tables in oracle

Updating two tables in oracle

The syntax for a multi-table select statement is as follows: Run that and see what you get. However, when I run the query, I get 2 rows for Rachel – one for her current phone number and another for her previous one. Of course we can simply add to our column list and look to see which record is current. END_DATE IS NULL” to our Where clause and exclude end-dated rows in that way. Expand the query to display our friends’ addresses: to do this you’ll need to join the FRIEND_ADDRESS and ADDRESS tables. You’ve probably already guessed that I’m setting you up, but it’s important that we make these mistakes now, so we can learn about them. But what if Rachel had told us that she was changing her phone number next month and we’d put in a future end-date? This doesn’t only happen when our Where clause is completely missing; the same thing would happen if we were joining 3 tables, but only included 2 in our Where clause or if we joined the tables ambiguously (always join using key columns where possible). Run the following statement: SELECT FRIEND_ID, FIRST_NAME, LAST_NAME, PHONE_NUMBER FROM FRIEND_NAME, FRIEND_PHONE, PHONE_NUMBER WHERE FRIEND_NAME. In fact, it is good practice to do this with all columns in a multi-table statement. Although if you had to type out the full table names each time you referred to a column in a long statement, you’ll soon be in hospital with RSI. So if you ever notice that your query is returning more rows that you anticipated, look for a Cartesian join. To get around this problem, you can use table aliases. PHONE_NUMBER FROM FRIEND_NAME FN, FRIEND_PHONE FP, PHONE_NUMBER PN WHERE FN. you may have to add an update trigger to the view itself. comment with the statement you are trying to run..feedback off;create table sales_order( order_id numeric(10,0),total numeric(8,2) );create table order_item(order_id numeric(10,0),quantity numeric(10,0),price numeric(8,2));insert into sales_order (order_id) values (1);insert into sales_order (order_id) values (2);insert into sales_order (order_id) values (3);insert into order_item (order_id, quantity, price) values (1,1,15.0);insert into order_item (order_id, quantity, price) values (1,2,10.0);insert into order_item (order_id, quantity, price) values (1,3, 5.0);insert into order_item (order_id, quantity, price) values (2,1,15.0);insert into order_item (order_id, quantity, price) values (2,2,15.0);insert into order_item (order_id, quantity, price) values (2,2, 5.0);insert into order_item (order_id, quantity, price) values (2,5,10.0);insert into order_item (order_id, quantity, price) values (3,3,15.0);update sales_orderset total = (select sum(quantity*price) from order_item where order_id = sales_order.order_id);select * from sales_order;drop table sales_order;drop table order_item; ORDER_ID TOTAL ---------------------- ---------------------- 1 50 2 105 3 45 update (select feed_year from FEEDBACK f inner join APPOINTMENTS ap on f.

The joins we’ve been using thus far are effectively simple inner joins.

PHONE_NUMBER FROM FRIEND_NAME FN, FRIEND_PHONE FP, PHONE_NUMBER PN WHERE FN. To do this I’ll need to tell you about outer joins.

But what if we wanted to see a full list of our friends with a null if they do not have a phone number?

If we consider what we’ve learned so far – Select, Update, Insert, Delete – as unicellular organisms, what we’re about to… In other words, we can say, we want to see all of our friends (all records in friend_name), and we don’t mind seeing nulls whenever they don’t have a phone number.

Continue Reading → Part 1, Part 2, Part 3 A wise man* once said: To build the Great Wall of China, you must start with a brick. There are two types of outer joins; a left outer join allows nulls in the second table in our join, while a right outer join allows nulls in the first table (while showing all records from the table on the right).

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