How to update a table with null values with data from other table at one time?

Question

I have 2 tables - A and B . Tbale A has columns -pkey(primary key) and col1.Tbale B has columns pr_key(primary key, not a reference key) and column1.Table B has no values,while table A is populated with 4 rows.I want to update table B taking exactly the same values as table A at one go. Please help!

Answer 1

Should be something like that (depends on SQL implementation you use, but in general, the following is rather standard. In particular should work in MS-SQL and in MySQL.

INSERT INTO tblB (pr_key, column1)
  SELECT pkey, col1
  FROM tblA
  -- WHERE some condition (if you don't want 100% of A to be copied)

The question is a bit unclear as to the nature of tblB's pr_key, if for some reason this was a default/auto-incremented key for that table, it could just then be omitted from both the column list (in parenthesis) and in the SELECT that follows. In this fashion upon insertion of each new row, a new value would be generated.

Edit: It appears the OP actually wants to update table B with values from A. The syntax for this should then be something like

UPDATE tblB 
SET Column1 = A.Col1
FROM tblA AS A
JOIN tblB AS B ON B.pr_key = A.pkey