sql - Update table values from another table with the same user name -
i have 2 tables, same column named user_name, saying table_a, table_b.
i want to, copy table_b, column_b_1, column_b2, table_b1, column_a_1, column_a_2, respectively, user_name same, how in sql statement?
as long have suitable indexes in place should work alright:
update table_a set column_a_1 = (select table_b.column_b_1 table_b table_b.user_name = table_a.user_name ) , column_a_2 = (select table_b.column_b_2 table_b table_b.user_name = table_a.user_name ) exists ( select * table_b table_b.user_name = table_a.user_name )
update in sqlite3 not support clause, makes little more work in other rdbms.
if performance not satisfactory, option might build new rows table_a using select , join table_a temporary table. delete data table_a , repopulate temporary.
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