Data Management:
First, the query data: select * from table name;
add data: insert into table;
change where condition data update table set field name = field value;
empty table: delete from table where conditions; delete table data, without deleting the table data structure, can be rolled back
truncate table show; delete table data, delete data structure of a table, not rollback
Second, the query:
query all columns: select * from table name
query specifies column: select set out in 1, 2 column names from the table name
from the alias: select 1 as set out in the custom column names, column names, column names from 2 Customize table were
merged column query: SELECT (column name + - * / column names) from table
III deduplication data query:
SELECT DISTINCT (column names) from table;
SELECT DISTINCT column names from table name;
IV paging query: limit start line, a few lines of the query
SELECT * FROM employee where conditions lIMIT 0,2;
Home = (this page -1) * number of lines per page
Note: in the query using the rearmost limit
V. query packet: column group by having the conditions to be grouped in
six sorting query: order by columns to be sorted