learning sql

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CREATE TABLE celebs (
  id INTEGER,
   name TEXT,
    age, INTEGER
);

1. CREATE TABLE clause tells SQL that you want to create a new table
2. celebs name of the table
3. (id INTEGER, name TEXT, age INTEGER) a list of parameters defining each column in the table and its data type

• id is the first column in the table.It stores values of data type INTEGER
• name stores values of data type TEXT
• age stores values of data type INTEGER

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INSERT INTO celebs (id, name, age) VALUES (1, 'William Turner');

This statement inserts new rows into a table. You can use the INSERT statement when you want to add new records.

1. INSERT INTO clause adds the specified row/rows
2. celebs name of the table the row is added to
3. (id, name, age) is a parameter identifying the columns that data will be inserted into
4. VALUES indicates the data being inserted
5. (1, 'William Turner, 21') is a parameter identifying the values being inserted

• 1 insert into id column
• William Turner inserted into name column
• 21 inserted into age column

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SELECT name FROM celebs;

SELECT statements are used to fetch data from a database. Here, SELECT returns all data in the name column of the celebs table.

1. SELECT clause indicates that the statement is a query
2. name specifies the column to query data form
3. FROM celebs specifies the name of the table to query data from

Query data from all columns in a table with SELECT.

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SELECT * FROM celebs;

* allows to select every column in a table without having to name each one individually.

SELECT statements always return a new table called the result set.

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UPDATE celebs SET age = 22 WHERE id = 1;

UPDATE statement edits a row in the table. To change existing records.

1. UPDATE edits a row in the table
2. celebs table name
3. SET indicates the column to edit
4. WHERE indicates which row(s) to update with the new column value.

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ALTER TABLE celebs ADD COLUMN twitter_handle TEXT;

The ALTER TABLE statement added a new column to the table.

1. ALTER TABLE lets you make the specified changes
2. celebs name of table
3. ADD COLUMN lets you add a new column to a table
   1. twitter_handle name of new column being added
   2. TEXT data type
4. NULL is a special value in SQL that represents missing or unknown data.

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DELETE FROM celebs WHERE twitter_handle IS NULL;

DELETE FROM statement deletes one or more rows from a table.

1. DELETE FROM lets you delete rows from a table
2. WHERE lets you select which rows you want to delete.
3. IS NULL a condition in SQL that returns true when the value is NULL and false otherwise