SQL.js

/**
 * SELECT       == queries data from a table.
 */


// * CREATE TABLE === creates a new table.
CREATE TABLE celebs (id INTEGER, name TEXT, age INTEGER);
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/**   //  * INSERT INTO == adds a new row to a table 
 * This INSERT statement inserts new rows into a table. 
 * You can use the INSERT statement when you want to add new records.
 */
INSERT INTO celebs (id, name, age) VALUES (1, 'Justin Bieber',   21);
INSERT INTO celebs (id, name, age) VALUES (2, 'Beyonce Knowles', 33); 
INSERT INTO celebs (id, name, age) VALUES (3, 'Jeremy Lin',   26); 
INSERT INTO celebs (id, name, age) VALUES (4, 'Taylor Swift', 26);
/**
 # INSERT INTO     === is a clause that adds the specified row or rows. 
 # celebs          === is the name of the table the row is added to. 
 # (id, name, age) === is a parameter identifying the columns that data will be inserted into. 
 # VALUES          === is a clause that indicates the data being inserted
 */

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/**    // * ALTER TABLE  == changes an existing table.
 * The ALTER TABLE statement added a new column to the table
 * You can use this command when you want to add columns to a table
 */
ALTER TABLE celebs ADD COLUMN twitter_handle TEXT; 
/**
 # ALTER TABLE    === is a clause that lets you make the specified changes. 
 # celebs         === is the name of the table that is being changed. 
 # ADD COLUMN     === is a clause that lets you add a new column to a table. 
 # twitter_handle === is the name of the new column being added
 # TEXT           === is the data type for the new column
 */
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/**  // * UPDATE  == edits a row in a table.
 * The UPDATE statement edits a row in the table.
 * You can use the UPDATE statement when you want to change existing records.
 */
UPDATE celebs 
SET age = 22 
WHERE id = 1; 

UPDATE celebs 
SET twitter_handle = '@taylorswift13' 
WHERE id = 4; 
/**
 # UPDATE === is a clause that edits a row in the table. 
 #             celebs is the name of the table. 
 # SET    === is a clause that indicates the column to edit.
 #   age is the name of the column that is going to be updated
 #      22 is the new value that is going to be inserted into the age column.
 # WHERE  === is a clause that indicates which row(s) to update with the new column value. 
 # Here   === the row with a 1 in the id column is the row that will have the age updated to 22.
 */

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 /**  //  * DELETE FROM  == deletes rows from a table.
  * The DELETE FROM statement deletes one or more rows from a table. 
  * You can use the statement when you want to delete existing records.
  */

DELETE FROM celebs WHERE twitter_handle IS NULL;
/**
 # DELETE FROM === is a clause that lets you delete rows from a table.
 # celebs      === is the name of the table we want to delete rows from.
 # WHERE       === is a clause that lets you select which rows you want to delete. 
 #                Here we want to delete all of the rows where the twitter_handle column IS NULL 
 # IS          === NULL is a condition in SQL that returns true when the value is NULL and false otherwise
 */
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