2. (5 pts) Assume two tables T3 and T4 have been created as follows. Table T4 ke

Question

2. (5 pts) Assume two tables T3 and T4 have been created as follows. Table T4 keeps track of the number of times (c) that a certain string (s) appears in table T3 create table T3 s varchar2 (100), x nimber, Y number primary key (x, y) create table T4 s varchar2 (100) primary key, c number, 0) For example, T3 contains computer database networking 7 graphics networking1 networking computer Then T4 should contain: computer database networking.3 graphics Write a trigger TriggerProblem2 such that every time a new record is inserted into table 73, table T4 should be updated accordingly. For example, after a row database. 5, 5) is inserted into table T3, table T4 should be changed to: computer database networking 3 graphics

Explanation / Answer

Following trigger will update the table T4 on inserting a record in table T3 as per the given condition.

First using the select query a records are count based on matching insertion, then the count is updated using the update statement in the T4 table.

CREATE TRIGGER update_t4

AFTER UPDATE ON T3

FOR each row

BEGIN

DECLARE updateCount INT;

        SET updateCount = ( SELECT COUNT(*) FROM T3 WHERE s = new.s );

        UPDATE T4 SET c = updateCount WHERE s = new.s;

END;

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