memorization 3

precision

the total number of digits a numeric column may store.

scale

specifies the exact number of digits that can be stored to the right of the decimal point for a numeric value

range

defines the minimum and maximum values that can be stored within a column, as determined by its data type

VARCHAR(n)

a data type that stores a string up to “n” characters longs, but will only use the minimum storage space necessary to do so.

CHAR(n)

is a data type that stores a string up to “n” characters long and always uses “n” characters of storage space to do so

DECIMAL(p,s)

is a data type that stores exact values of numbers with a specific number of total digits and specific number of digits to the right of the decimal point.

INT

is a data type that stores whole numbers.

DATETIME

is a data type that stores the value of an hour, minute and second for a year, month and day

Data Definition Language (DDL) statements

are SQL commands used to create, modify, and delete the structure of database objects.

Data Manipulation Language (DML)

statements are SQL commands used to insert, retrieve, modify, and delete data stored within the database objects.

Data Query Language (DQL)

SQL commands used to retrieve and view data from a database.

Data Control Language (DCL)

SQL commands used to manage user permissions and access rights to the database and its objects

USE {database name}

will display the name of all databases that you have access privileges for

SHOW TABLES

display the name of tables in the currently selected database.

SHOW COLUMNS FROM

will display the information about the columns within a table

DESCRIBE

display the information about the columns within a table.

CREATE DATABASE

will add a new database on a database server.

DROP DATABASE

will remove an existing database on a database server.

column property

may define a column’s name, data type and options.

constraint property

may define a constraint with a name, type, and options.

CREATE TABLE {table name}

add a new table to the currently selected database.

DROP TABLE {table name}

remove an existing table in the currently selected database.

ALTER TABLE {table name}

will modify the structure of a table.

ADD COLUMN {column definition}

add a column to a table.

DROP COLUMN {column_name}

will remove a column from a table

MODIFY COLUMN {column_definition}

can change the column properties of a column in a table.

CHANGE COLUMN {old_column_name}

can change the column properties of a column in a table including renaming that column.

ADD CONSTRAINT {constraint_name}

can add a constraint to a table.

RENAME {new table name}

will rename a table.