MySQL Update old data

Scene:

There are two of the following tables

TableA

Id	ROW1	ROW2	ROW3	ROW4
1	2	3	4	5

TableB

Id	rowa_id	Rowa_row4
1	2

At the beginning of the table B only ID, rowa_id two fields, for some convenience reasons, and so on, now to add a field "Rowa_row4", now to the previous records to supplement the corresponding ROWA_ROW4 data;

Analysis:

My first thought was to write a piece of Java code that loops out the data from the TableA and deposits it into the tableb;

Later Raigo gave a simple SQL solution, as follows.

SQL code

--Set not auto commit

SET AUTOTATBT = 0;

--Update data

UPDATE TableB TB

SET TB. Rowa_row4= (

SELECT ROW4 from TableA ta WHERE ta.id= TB. ROWA_ID);

--whether the query achieves the effect

SELECT * from TableA TA, TableB TB where ta.id= TB. rowa_id;

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MySQL Update old data