Union： It represents the connection of two queries, The requirements are two select Have the same columns, But repeated will only keep one
INSERT INTO MYSQL FULL
Right join： There is a connection, Based on the table on the right, Even if the data on the left doesn't match, If the data on the left is empty, it will also returnįull join： Full connection, All data will be returned, Only the data in the table, whether it is matched or not, Will return to Left join： Left connection, The two tables take the table on the left as the benchmark to get the connected data, If the data in the right table does not match, If the data on the right is empty, it will also return Join Internal connection, Connect the two tables according to the same key, Get is intersection, That is, both tables have data of this key As an excellent developer ,SQL I almost forgot, This is really a sin ！ It will be used later, Learn a little every day, Slowly, it will also be SQL Boy！įirst understand what is join（inner join）,left join,right join,full join,union, union all
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