SQL statement, judge the number size, greater than a certain value minus a set value

  mysql, question

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Find a SQL statement, as shown in the figure meta_value value is greater than 70, automatically let him minus 70

For example:

56, then the same
78, then 78-70, let him become 8

Add: thank you, add a judgment condition, meta_key must be “views” to use the above subtraction

UPDATE tblname SET field=field-70 WHERE field>70