从一个表动态获取行并从其他表获取值将其汇总并插入到目标表中

Question

x table has columns(Agency,datac)
Y table has columns(Agencyname,total)
EXAMPLE

Agency | datac
NET    | 100 
GOO    | 300 
NET    | 100 
GOO    | 100 

Agencyname | total
NET        |  
GOO        | 

first customer adds Agencyname then it gets update on table Y
From a dropdown menu in html i have made user to either choose NET OR GOO but what i want is how many values they may enter in table X.
i want their total sum to be inserted into table Y. so that my expected output looks like this

Agencyname | total
NET        | 200
GOO        | 400

Answer 1

The most straight forward way is probably an update with a subquery;

UPDATE TableY
SET total = (SELECT SUM(datac) FROM TableX WHERE Agency=AgencyName)

An SQLfiddle to test with.