CpSc 3220 The Language of SQL Chapter 17 Modifying Data

SQL handles CRUD operations The DML part of the SQL language allows the implementation of all CRUD operations C - create: handled by the INSERT statement R – retrieve: handled by the SELECT statement U – update: handled by the UPDATE statement D – delete: handled by the DELETE statement

The INSERT statement INSERT statements allow in insertion of rows of data into an existing table Each inserted row must be unique, i.e., it must contain the primary key Some tables are defined to have auto-increment PKs and the DBMS will insert those values automatically Values need not be inserted for all columns, columns for which no value is inserted are set to NULL Insertions can be constrained by tables rules; i.e., PK and FK constraints

Basic Forms of the INSERT statement There are two basic types of INSERT statements 1.Insert specific data that is included explicitly in the INSERT statement 2.Insert data that is obtained from a SELECT statement (a subquery)

General Format for Type One INSERT INSERT INTO tableName [(columnList)] VALUES (row1Values) [,(row2Values)...] ;

Example of Type One INSERT INSERT INTO Student (ID, name, dept_name, tot_cred) VALUES ('12127','Howard','Comp. Sci.','0') ;

Example of Type One INSERT insert into student values ('54444','Wilson','Comp. Sci.', '0');

Example of Type One INSERT insert into student (ID,name,tot_cred) values ('44499','Wilson', '0');

Example of Type One INSERT insert into student (name,ID,tot_cred) values ('Bixby','44999', '0');

Example of Type One INSERT INSERT INTO Student (ID, name, dept_name, tot_cred) VALUES (12127,’Howard’,,0) ;

Example of Type One INSERT INSERT INTO Student (ID, name, tot_cred) VALUES (12127,’Howard’,0) ;

Example of Type One INSERT INSERT INTO Student (ID, tot_cred, name) VALUES (12127, 0, ’Howard’) ;

Example of Type One INSERT insert into student values ('64445','Wilson','Comp. Sci.', '0'), ('74446','Jackson','Comp. Sci.', '0'), ('74447','George','Comp. Sci.', '0'), ('74440','James','Comp. Sci.', '0'), ('74440','Andrews','Comp. Sci.', '0');

Error in Type One INSERT insert into student values ('64445','Wilson','Comp. Sci.', '0'), ('74446','Jackson','Comp. Sci.', '0'), ('74447','George','Comp. Sci.', '0'), ('74440','James','Comp. Sci.', '0'), ('74440','Andrews','Comp. Sci.', '0');

Error in Type One INSERT insert into student values ('64445','Wilson','Comp. Sci.', '0'), ('74446','Jackson','Comp. Sci.', '0'), ('74447','George','Comp. Sci.', '0'), ('74440','James','Comp. Sci.', '0'), ('74448','Andrews','CompSci.', '0');

General Format for Type Two INSERT INTO tableName [(columnList1)] SELECT columnList2 FROM tableName2 WHERE condition;

Example of Type Two INSERT insert into student (ID,name,dept_name,tot_cred) select i.id,i.name,'Comp. Sci.','0' from instructor as i where dept_name='History';

The DELETE statement Even simpler than the UPDATE General form DELETE FROM tableName [WHERE condition] There is an alternate form to delete an entire table: TRUNCATE TABLE tableName

The UPDATE statement A bit more complex We must specify the columns to be updated, give an expression that specifies the update, and include logic for determining which rows are to be updated. All data can be supplied in the UPDATE statement Some data may be determined by subqueries

General Form of an UPDATE statement UPDATE table SET colName1 = expression1 [,colName2 = exp2... ] WHERE condition

An Example of an UPDATE statement UPDATE instructor SET salary = salary * 1.5 WHERE dept_name = 'Comp. Sci.';

Another Example of an UPDATE statement UPDATE takes SET grade = 'A+' WHERE course_id = 12345;

That’s It! You know all the CRUD about SQL, the DML part But you don’t know how to create at database That’s what we look at next; the DDL part of SQL Read Chapter 18 of the Rockoff textbook