plsql - Replace the value -

we have column 'a' in 'x' , 'y' table. if value of column 'a' not null need consider in 'x' table otherwise need consider in 'y' table.

based on requirement how achieve it?

thanks in advance

sounds you're asking nvl function. based on limited information go on work you...

create table x(id int, varchar(255)); insert x(id, a) values(1, 'one'); insert x(id, a) values(2, null); insert x(id, a) values(3, 'three');  create table y(id int, varchar(255)); insert y(id, a) values(1, 'one'); insert y(id, a) values(2, 'two'); insert y(id, a) values(3, 'three');  select x.id, nvl(x.a,y.a) x, y x.id = y.id; 

results in...

id  ========== 1   1 2   2 3   3