21  other commands: update/delete, create/drop/insert

As we’ve seen, the SQL SELECT command is used to retrieve data from a database in many different forms. This is by far the most important SQL command for a data analyst to know. However there are numerous other sql commands. The following gives a brief overview of many of those commands.

21.1 db-fiddle website

sqldf cannot run SQL commands other than SELECT.

We will use the following website to demonstrate other SQL commands.

Just create the database on db-fiddle


some sample select statements with the same tables


21.2 update

The UPDATE command is used for modifying the data in a table. See the following for more info:

21.3 delete

The DELETE command is used to delete entire rows of data from a table. See the following for more info:

21.4 create table

The CREATE TABLE command is used to create tables in a relational database. See the following for more info:

As part of the create table command, you can specify certain “constraints” on the columns of the table. For example, you can specify that a particular column or columns should never be allowed to contain any NULL values or that all of the values in a particular column should be unique (in addition to this requirement for the primary key). See the following for info about how to apply various constraints to the columns in a table:

21.5 insert a new row into a table

The INSERT command is used to insert one or more new rows into a table. See the following for more info:

21.6 drop table

The DROP TABLE command removes an entire table (including the structure of the table and all rows of data) from a database. See the following for more info:

21.7 SQL “DML” vs “DDL” commands

The commands in SQL are often categorized into the following two distinct categories:

21.7.1 Data Manipulation Language (DML) SQL commands

The commands in SQL that are used for creating, reading, updating and deleting data (collectively referred to as “CRUD” operations) are known as “Data Manipulation Language” (DML) SQL commands. These include the following SQL commands:

  • insert (for “creating” rows of data)
  • select (for “reading” rows of data)
  • update (for “updating” rows of data)
  • delete (for “deleting” rows of data)

The term DML or “Data Manipulation Language” is often misunderstood. DML is NOT a new language. DML is simply the term that is used to refer to the parts of SQL for “manipulating” data (i.e. performing CRUD operations).

21.7.2 Data Definition Language (DML) SQL commands

The commands in SQL that are used for creating and managing the database tables are known as “Data Definition Language” (DML) SQL commands. These include the following.

  • CREATE TABLE - used to create a table
  • DROP TABLE - used to destroy an entire table (its structure and its data)
  • ALTER TABLE - used to change the structure of a table (e.g. add columns)

Many RDBMS products include other DDL commands for example to rename tables as well as to work with other more advanced structure. For more info, see the documentation for your particular RDBMS product.

# There are many SQL commands other than select.
# The following is a list of some of the more common SQL commands. 
# The list below doesn't include the entire syntax. 
# See this page for more info on the syntax for individual
# SQL commands: https://www.w3schools.com/sql/default.asp
#  # create a new table structure
#  # see : https://www.w3schools.com/sql/sql_create_table.asp
#  CREATE TABLE someTable ...
#  # "drop" or entirely remove the table structure and all rows of data
#  DROP TABLE someTable    
#  # Insert a new row into a table
#  INSERT INTO someTable ...
#  # modify the values in a table
#  UPDATE someTable ...
#  # delete some or all of the rows in a table
#  DELETE FROM someTable ...
# THE VARIOUS FILES CONTAINED IN cateringDatabase-v003.zip