Basic query:
select * from table name;
Basic condition query:
select * from Table name where conditions;
Fuzzy query:
select * from table name where name …like ‘%device%’; Query all the devices that contain ”Information;
select * from table name where name like’device%’; query all the information that starts with device in the name;
select * from table name where name %Device ‘; query all information ending with device in name;
select * from table name where name like like ‘%装%置% ‘; Query all the information that contains the sequence name of “installation” (before) and “location” (behind) in the name; for example: “Switchdevice “, but cannot find out “置装 switch”;
select * from table name where name, like, _置_, Query All names in the name are three words and the middle is “location” information; “_” represents a single arbitrary character;
can’t find out a comment for now, and then find out the reason and then talk about it # select * from table where name like ‘[lights installed]’; query for all name with” “information; for example:” loaded “or a” lamp unit “” light switch “; < /span>
Sorting query:
select * from table name where name =’device’ order by id asc; Query all the information whose name is equal to the device and arrange them in order according to id;
select * from table name where order by id= device; The name is equal to the information of the device and is arranged in reverse order according to the id;
For group query and aggregation functions, see:
Aggregate function query: https://www. cnblogs.com/ncwoniu/p/11589200.html
Paging query:
select * from t_student where st_name like’%张%’ order by st_id limit 0 ,10; query the information that contains “Zhang” in the name, and the 10 data starting from the first will be displayed after the id is sorted; the paging query must be sorted first
Inner connection:
select * from Table 1 Join Table 2 on Table1.id = Table2.id; Query the intersection of the data in Table 1 and Table 2 that meet the conditions after on;
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External connection:
Left connection:
select * from table 1 left join table 2 on table 1.id = table 2.id; after the query matches on The intersection of the data in Table 1 and Table 2 of the conditions Add the remaining data in Table 1 on the left;
right connection:
select * from Table 1 right join Table 2 on Table 1.id = Table 2.id ; Query the intersection of the data in Table 1 and Table 2 that meet the conditions of on Add the remaining data in Table 2 on the right;
Multi-table connection:
select Table1.id, Table1.name, Table2.name from Table1, Table2 where Table1.id = Table2 .id;