Common sql statements:
Delete data in a table:
delete from table name;
delete from table name where field value='';
Add a piece of data:
insert into table name (field 1, field 2, field 3) values (value 1, value 2, value 3)
Query all data in the table:
select * from table name
Query the data in the table that meets the conditions:
select * from table name where field value = '';
Modify the value of a field in the table:
update table name set field='value' where condition;
Add a column to the created table
alter table table name add column column name varchar(20) not null;
Delete a column in the created table
alter table table name drop column column name;
Modify the size of the fields in the
table alter table table name modify(field value varchar(4000));