MySQL: Update a full table, inserting a MD5 hash, for each row a specific one

Try this:

UPDATE yourtableSET hash = MD5(name)WHERE hash IS NULL

Note that the test is hash IS NULL and not hash = NULL as you wrote in your question.

mysql sql sql-update md5

No need write an extra query for update.

Just go to table design
create a new column
select new created column, below you'll get properties
Find for computed Column Specification
Under above opt you'll find formula section write HashBytes([Algo], [ColumnName])

it will automatically create an hash value for rows which are already present.

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