soft article release various situations and categories of connection queries in the connection, including inner and outer connections. inner connection queries refer to querying only the data that exists on the left and right tables. based on the foreign key relationship, data that meets the conditions is filtered out from the cartesian product. inner connection queries can be implemented in two forms, left join query, i.e. 1 continuously open 50 people
warm tip: make a friendly link to this website on your website, and you can automatically include it once and automatically rank first in this website! RCS) comprehensive other