show databases; // list all databases
select databases; // display the current database
create database database name; // create a database
drop database database name; // delete the database
show full tables; // View table structure (Display all)
show open tables; // include cache table and open when the non-temporary table
show table status; // Display status
DDL:
create database test character set utf8; // create the database and set the character set
alter table table add Column Name Data Type; // add a
desc table name; // Check table field information
alter table table name drop column names; // delete a
rename table the original table name to the modified name; // modify the table name
show cretae table table name; // see the table creation statements
alter table table name character set encoding; // Modify Character Encoding
alter table change table column names new original Column Name Data Type; // Modify Listing
drop table table name; // Delete table
DML:
insert into table (table columns) values (); // Insert
set update table column name = value where the new condition; // Review
delete from table [where name = Column column value]; // delete
truncate table table name; // Empty Table
1. delete the data deleted table, the table structure is still, you can retrieve deleted data
2. truncate table to delete, right directly drop, and then create a new table of the same, can not recover deleted data, perform faster than delete,
The reason execute faster:
Because delete delete delete process is that each row from the table, and at the same time the behavior of the delete operation and then saved as a transaction log records for rollback
truncate then delete all data from a table
Paradigm:
The first paradigm: Each column of the data table (Attribute) are substantially inseparable data items, each of each column of data are required to store only a single value, but
The second paradigm: all data requirements of every data table and the primary key of the data are entirely dependent relationship
Third Normal Form: All non-key attributes and only candidate key correlated, which means that all non-key attributes should be independent of each other.
Anti paradigm:
Trying to process the redundant data, or by increasing the data packets to optimize the database reads of
show varianles like '% query_log%'; see slow log is turned on (all over log_query_time seconds execution time sql statement will be recorded in the slow query log)