D create or replace table t as (select 'This is a string' as s);

D from t;
┌──────────────────┐
│        s         │
│     varchar      │
├──────────────────┤
│ This is a string │
└──────────────────┘

# Now make two copies.
D create or replace table tt as (select s as s1, s as s2 from t);

D from tt;
┌──────────────────┬──────────────────┐
│        s1        │        s2        │
│     varchar      │     varchar      │
├──────────────────┼──────────────────┤
│ This is a string │ This is a string │
└──────────────────┴──────────────────┘

# Change s2 and then verify that s1 is unaltered
D UPDATE tt SET s2 = s2[1];

D from tt;
┌──────────────────┬─────────┐
│        s1        │   s2    │
│     varchar      │ varchar │
├──────────────────┼─────────┤
│ This is a string │ T       │
└──────────────────┴─────────┘

# Check that s and s1 are also still equal
D select s = s1 from t positional join tt;
┌──────────┐
│ (s = s1) │
│ boolean  │
├──────────┤
│ true     │
└──────────┘