How to replace name with number ID

Question

Example:
Table1
T1ID Name1
1 John Smith
2 Kathy Smith
Table2
T2ID Name2
100 John Smith
101 Kathy Smith
102 John Smith
103 Kathy Smith
I want to replace all names in column called Name2 in Table 2, with matching T1ID from Table 1. There are many name repetitions in Table 2.

Answer 1

If Name2 is VARCHAR and T1id is number then it would be better to add a new column with a consistent data type;
Sample data;
create table table1 as (
select 1 t1id, 'John Smith' name1 from dual union all
select 2, 'Kathy Smith'from dual);
Table created
alter table table1 add constraint table1_pk primary key (t1id);
Table altered
create table table2 as (
select 100 t2id, 'John Smith' name2 from dual union all
select 101, 'Kathy Smith' from dual union all
select 102, 'John Smith' from dual union all
select 103, 'Kathy Smith' from dual);
Table createdAdd the new column;
alter table table2
   add name_id references table1(t1id);
Table alteredUpdate the new column;
merge into table2 t2
using (select t1id, name1
       from table1) t1
on (t2.name2 = t1.name1)
when matched then
  update
  set t2.name_id = t1.t1id;
DoneDrop the retired column;
alter table table2 drop column name2;
Table altered
select * from table2;
      T2ID    NAME_ID
       100          1
       101          2
       102          1
       103          2