1.create database name; create a database
use name; use database
2.create table name（
column name + constraint
column name + constraint
column name + constraint
......
column name + constraint
) create table
3 Commonly used sentences are: add, delete, modify and check
Add statement: insert into table name values (data, data, data,)
Delete statement: delete from table name where condition
Modify statement: Update table name set column name = value, column name = value where condition
Query statement: select * from table name
order by sorting (desc descending asc ascending).
group by grouping can be grouped as needed.
Inner connection table name inner join table name on condition.
Outer join (left outer right outer) table name left (right) outer join table name on condition
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