Database transaction differences: can be committed read and read-repeat differences

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MySQL default thing is repeat read (REPEATABLE read isolation level),
Postgres default things are read Committed isolation level, and now compare their differences according to the instance.

Mysql:

Left for thing 1, right for thing 2.

The first step:

Things 1 queries, things 2 queries, and their query results are consistent.

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Step Two:

Things 1 Update-query-but do not commit, things 2 query, their results inconsistent

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Step Three:

Things 1 commits-queries, things 2 queries, their results are inconsistent ——— actually the difference between the 2 things is here.

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Fourth Step:

Things 1 queries, things 2 commits-queries, their results are consistent
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Postgresql:

Left for thing 1, right for thing 2

The first step:

Things 1 query, things 2 query, query results are consistent.

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Step Two:

Things 1 Modification-queries, things 2 queries, inconsistent query results

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Step Three:

Thing 1 Commit-query, Thing 2 query, query results consistent

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Fourth Step:

Things 1 Query, things 2 submit query, the result is consistent, no

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Database transaction differences: can be committed read and read-repeat differences