They generally work under an alias, a username. On the web, most people don’t necessarily use their real name. New columns can be added to a table using ALTER.
WHERE name = 'Bart Simpson' OR name = 'Homer Simpson' ALTER We can run the following query: DELETE FROM comments
We are in a need to delete all comments that are posted by ‘Bart Simpson’ and ‘Homer Simpson’. We can enter the command: DELETE FROM comments Suppose we need to delete a row with post_id 9. To DELETE row(s) from the table we can use the WHERE condition, just like in UPDATE. It is defined as a PRIMARY KEY and will always be unique.
ACCESS SQLITE DATABASE UPDATE
For every name = ‘Shivam Mamgain’ the email will be set to To update a particular row use the post_id attribute. This will change the email attribute for the name ‘Shivam Mamgain’ to The name attribute is not unique, so the above statement may affect more than one row. SET email = WHERE name = 'Shivam Mamgain' Issue the following statement: UPDATE comments Suppose email for ‘Shivam Mamgain’ was changed to. Note: Select a mode of display that suits you. To overcome this, we must alter some parameters. The resultant table might look obfuscated without headers and proper separation between columns. This will retrieve all rows from the table. The above statement can also be written as: SELECT * FROM comments SELECT post_id, name, email, website_url, comment FROM comments To retrieve data we use the SELECT command. We have learned to insert data into the table. The thing is, it is not needed because it is an AUTOINCREMENT field.Įnter some more rows in the table to practice. I have not provided the value for post_id, even though it is defined as NOT NULL. INSERT INTO comments ( name, email, website_url, comment ) VALUES ( 'Shivam Mamgain', , '', 'Great tutorial for beginners.' ) Suppose a user has entered a comment with the details: Name : Shivam Mamgain Now that the table has been created, we need to enter data. Note: To get the schema of the table enter. To check if table has been created, issue the meta command. PRIMARY KEY 3 and AUTOINCREMENT 4 elaborate the post_id attribute. NOT NULL makes sure that the particular value is not left empty in a record. Website_url TEXT NULL, comment TEXT NOT NULL ) Post_id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT , To create it, enter the statement: CREATE TABLE comments ( To store the comments we must define a table. It is what happened when we entered the single command sqlite3 for the first time. Note: If no filename follows the command, sqlite3 automatically creates a temporary database. This will create a database file comment_section.db in the current working directory. Then, issue the command: sqlite3 comment_section.db If you are still in the sqlite3 program, quit it by entering. Most other database engines including MySQL use Static Typing. You can see the documentation for different Datatypes and Storage Classes provided in SQLite3. We can define the datatypes of the columns (attributes) as follows: Attribute We must also define a column that numbers the comments. Of the four of these, only website URL is optional. To post a comment, the user must enter the following details: Almost every website today has a comment section.
We will learn to work with sqlite3 with our Comment Section database. They can be stored on various storage devices and can be transferred across different computers.
ACCESS SQLITE DATABASE PORTABLE
SQLite databases are cross-platform portable files. Since the tutorial is a beginner level introduction, we will cover only the above mentioned commands. Note: SQLite understands many other standard commands, a list of which can be read here. Standard Commands can be classified into three groups:ĭata Definition Language: It provides the storage structure and methods to access data from the database system.ĭata Manipulation Language: It enables users to manipulate (add/modify/delete) data.ĭata Query Language: It enables users to retrieve required data from the database. Standard SQL commands are issued to operate on a database. Meta commands are issued to examine a database. Let us go through the standard commands in sqlite3.