--- title: SQL Update Query --- ## SQL Update Query ### What an Update query can do An update query gives the DBA or SQL-using programmer the ability to update many records with one command. Important Safety Tip! Always have a backup copy of what you are about to change BEFORE you change it! This guide will: * add a new field to the student table * test the logic to update that field with a school assigned email address * update the new field. Here is the student table as we start this process ```sql SELECT * FROM student; ``` ```text +-----------+------------------------+-----------+------------------+---------------------+---------------------+ | studentID | FullName | sat_score | programOfStudy | rcd_Created | rcd_Updated | +-----------+------------------------+-----------+------------------+---------------------+---------------------+ | 1 | Monique Davis | 400 | Literature | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 2 | Teri Gutierrez | 800 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 3 | Spencer Pautier | 1000 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 4 | Louis Ramsey | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 5 | Alvin Greene | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 6 | Sophie Freeman | 1200 | Programming | 2017-08-16 15:34:50 | 2017-08-16 15:34:50 | | 7 | Edgar Frank "Ted" Codd | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 | | 8 | Donald D. Chamberlin | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 | | 9 | Raymond F. Boyce | 2400 | Computer Science | 2017-08-16 15:35:33 | 2017-08-16 15:35:33 | +-----------+------------------------+-----------+------------------+---------------------+---------------------+ 9 rows in set (0.00 sec) ``` ### Alter the table and add a new field ```sql ALTER TABLE `fcc_sql_guides_database`.`student` ADD COLUMN `schoolEmailAdr` VARCHAR(125) NULL AFTER `programOfStudy`; ``` The student table after the alter is executed. ```text mysql> SELECT FullName, sat_score, programOfStudy, schoolEmailAdr FROM student; +------------------------+-----------+------------------+----------------+ | FullName | sat_score | programOfStudy | schoolEmailAdr | +------------------------+-----------+------------------+----------------+ | Monique Davis | 400 | Literature | NULL | | Teri Gutierrez | 800 | Programming | NULL | | Spencer Pautier | 1000 | Programming | NULL | | Louis Ramsey | 1200 | Programming | NULL | | Alvin Greene | 1200 | Programming | NULL | | Sophie Freeman | 1200 | Programming | NULL | | Edgar Frank "Ted" Codd | 2400 | Computer Science | NULL | | Donald D. Chamberlin | 2400 | Computer Science | NULL | | Raymond F. Boyce | 2400 | Computer Science | NULL | +------------------------+-----------+------------------+----------------+ 9 rows in set (0.00 sec) ``` ### TESTING the logic (VERY important step!) ```sql SELECT FullName, instr(FullName," ") AS firstSpacePosition, concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu") AS schoolEmail FROM student; ``` ```text +------------------------+--------------------+------------------------+ | FullName | firstSpacePosition | schoolEmail | +------------------------+--------------------+------------------------+ | Monique Davis | 8 | Monique@someSchool.edu | | Teri Gutierrez | 5 | Teri@someSchool.edu | | Spencer Pautier | 8 | Spencer@someSchool.edu | | Louis Ramsey | 6 | Louis@someSchool.edu | | Alvin Greene | 6 | Alvin@someSchool.edu | | Sophie Freeman | 7 | Sophie@someSchool.edu | | Edgar Frank "Ted" Codd | 6 | Edgar@someSchool.edu | | Donald D. Chamberlin | 7 | Donald@someSchool.edu | | Raymond F. Boyce | 8 | Raymond@someSchool.edu | +------------------------+--------------------+------------------------+ 9 rows in set (0.00 sec) ``` *A note about concat(): in MySQL this command is used to combined strings, not so in other SQL versions (check your manual). In this usage it works like this: The substring of the FullName field up to but not including the first space is combined with "@someSchool.edu". In the real world this would HAVE TO be much more complex and you would need to ensure that the email address is unique.* ### Doing the update We'll pretend that this is what we want and update the table with this information: ```sql UPDATE student SET schoolEmailAdr = concat(substring(FullName,1,instr(FullName," ")-1),"@someSchool.edu") WHERE schoolEmailAdr is NULL; ``` Success! ```text mysql> SELECT FullName, sat_score, programOfStudy, schoolEmailAdr FROM student; +------------------------+-----------+------------------+------------------------+ | FullName | sat_score | programOfStudy | schoolEmailAdr | +------------------------+-----------+------------------+------------------------+ | Monique Davis | 400 | Literature | Monique@someSchool.edu | | Teri Gutierrez | 800 | Programming | Teri@someSchool.edu | | Spencer Pautier | 1000 | Programming | Spencer@someSchool.edu | | Louis Ramsey | 1200 | Programming | Louis@someSchool.edu | | Alvin Greene | 1200 | Programming | Alvin@someSchool.edu | | Sophie Freeman | 1200 | Programming | Sophie@someSchool.edu | | Edgar Frank "Ted" Codd | 2400 | Computer Science | Edgar@someSchool.edu | | Donald D. Chamberlin | 2400 | Computer Science | Donald@someSchool.edu | | Raymond F. Boyce | 2400 | Computer Science | Raymond@someSchool.edu | +------------------------+-----------+------------------+------------------------+ 9 rows in set (0.00 sec) ``` As with all of these SQL things there is MUCH MORE to them than what's in this introductory guide. I hope this at least gives you enough to get started. Please see the manual for your database manager and have fun trying different options yourself.