Update between two SQL tables: update the fields of the other table with the fields of one table

SQLmdash; mdash; update between two tables: update the fields of the other table with the fields of one table

SQLmdash; mdash; update between two tables: update the fields of the other table with the fields of one table

-- 1. This statement is equivalent to a Left join statement. The where clause is the number of updates.

-- Note! If the number of rows in the table (obtained after where) is smaller than that in the outer table (obtained after where), a record that does not meet the = condition will be assigned a null value.

-- If NULL values are not incorrectly assigned, AN in (select...) must be added to the External table to force the records of the internal and external tables to be consistent.

-- 2. This method is easy and error-prone.