Sqlite3 introduction and application of commonly used query statements sqlite3 database introduction SQLite database is a very lightweight self-contained (lightweightandself-contained) DBMS, Which is portable, easy to use, very small, efficient and reliable. SQLite is embedded into applications that use it. They share the same process space, rather than a single
Sqlite3 introduction and commonly used query statement application sqlite3 database introduction SQLite database is a very lightweight self-contained (lightweight and self-contained) DBMS, Which is portable, easy to use, very small, efficient and reliable. SQLite is embedded into applications that use it. They share the same process space, rather than a single
Sqlite3 introduction and application of common query statements
Sqlite3 database Introduction
SQLite database is a lightweight and self-contained DBMS. It is portable, easy to use, small, efficient, and reliable.
SQLite is embedded into applications that use it. They share the same process space, rather than a separate process. From the external perspective, it is not like an RDBMS, but inside the process, it is complete, self-contained database engine.
One of the major advantages of an embedded database is that you do not need network configuration or management in your program. Because the client and server run in the same process space.
SQLite database permissions only depend on the file system, without the concept of user accounts. SQLite has database-level locking and no network server. It requires memory usage, but other expenses are very small. It is suitable for embedded devices. All you need to do is compile it correctly into your program.
Sqlite commonly used query statements
Create a database using SQLite
SQLite is very convenient to use. You only need to input the "sqlite3" command with the name of the SQLite database. If the file does not exist, a new (database) file is created. Then, the sqlite3 program prompts you to enter SQL. The SQL statement is ended with a semicolon (;). After you press the Enter key, the SQL statement is executed. For example, create an SQLite database that contains the "user. db" table "cars.
CREATE command:
Create Database user. db
Sqlite3 user. db
Create Table cars
Create table carsl (name varchar (10), years smallint, price float );
Query a table
. Table
Insert data
Insert into cars values ('audi ', 1994,530 000.5 );
Insert into cars values ('volv', 2001,303 478.5 );
Display Header
. Header on
Modify Display Mode
. Mode column
Query data
Select * from cars; // query all data in the cars table
Sqlite> select * from tbl1 where one = 'xxx ';
Delete all statements
Sqlite> delete from cars;
Update statement
Sqlite> update cars set name = 'kaka 'where name = "mini ";
Delete statement
Sqlite> delete from cars where name = "kaka ";
Sqlite> delete from cars; // delete all data in the cars table
Conditional statement application "and" "or" "and or"
Sqlite> delete from cars where name = "volvo" or name = "audi ";
Sqlite> delete from cars where name = "volvo" and price = 324200;
Sqlite> delete from cars where (name = "volvo" or name = "audi") and price = 324203;
Display result:
Its operations are not much different from common relational databases, so it is convenient to add, delete, modify, and query data.
SQLite can display the query results in eight ways, which greatly facilitates data processing. The sqlite3 program can display the query results in eight different formats:
. Mode MODE? TABLE? Set output mode where MODE is one:
Csv Comma-separated values
Column Left-aligned columns. (See. width)
Html HTML
Insert SQL insert statements for TABLE
Line One value per line
List Values delimited by. separator string
Tabs Tab-separated values
Tcl TCL list elements
Usage:. mode column (switch the output format to row mode, for example)
SQLite3 Import and Export Database
Export Database
Sqlite>. databases (display database)
Sqlite>. backup main user. SQL (back up the database main, that is, copying the database)
Sqlite>. backup user2. SQL (backup default database main)