Creating database using sql commands
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The document provides information on various SQL commands used to create and manage databases and tables. It explains how to use SHOW, CREATE DATABASE, USE, SHOW TABLES, CREATE TABLE, DESCRIBE, ALTER TABLE, SELECT, UPDATE, DELETE, INSERT, CREATE VIEW commands. It also discusses table constraints like NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY and provides examples of how to implement them in CREATE TABLE and ALTER TABLE statements.
![ALTER TABLE statementALTER TABLE is use to modify an existing columnIt is consists of ADD, MODIFY and DROP columnALTER TABLE statement:ADD column MODIFY column DROP columnALTER TABLE tableADD (column datatype [DEFAULT expr][column datatype]….);ALTER TABLE tableMODIFY (column datatype [DEFAULT expr][column datatype]….);ALTER TABLE tableDROP (column datatype [DEFAULT expr][column datatype]….);](https://image.slidesharecdn.com/creatingdatabaseusingsqlcommands-110413110942-phpapp02/85/Creating-database-using-sql-commands-8-320.jpg)
![FROM identifies which tableSELECT [DISTINCT] {*, column,…}FROM table;](https://image.slidesharecdn.com/creatingdatabaseusingsqlcommands-110413110942-phpapp02/85/Creating-database-using-sql-commands-35-320.jpg)
![The WHERE clause follows the FROM clauseSELECT [DISTINCT] {*, column,…}FROM tableWHERE condition(s);](https://image.slidesharecdn.com/creatingdatabaseusingsqlcommands-110413110942-phpapp02/85/Creating-database-using-sql-commands-39-320.jpg)
Creating database using sql commands
- 1. CREATING DATABASE USING SQL COMMANDS
- 2. SHOW DATABASEmysql> SHOW DATABASES;Use the SHOW statement to find out what databases currently exist on the serverSQL command
- 3. CREATE DATABASEmysql> CREATE DATABASE newdb;Database nameCreate statementThe new database will appear after successfully create the database
- 4. USE DATABASEmysql> USE newdbCreating a database does not select it for use; you must do that explicitly.Note that USE, like QUIT, does not require a semicolon. The USE statement is special in another way, too: it must be given on a single line. SQL commandDatabase name
- 5. SHOW TABLESmysql> SHOW TABLES;To create one or more tables in the current database, you can use CREATE TABLE statement.SQL commandIt indicates that there is no table in the database.
- 6. CREATE TABLEmysql> CREATE TABLE Use a CREATE TABLE statement to specify the layout of your table.In this case, table pelajarwill have 4 attributes.
- 7. If you want to find out about the structure of a table, the DESCRIBE command is useful; it displays information about each of a table's columnsDESCRIBESQL commandDatabase name
- 8. ALTER TABLE statementALTER TABLE is use to modify an existing columnIt is consists of ADD, MODIFY and DROP columnALTER TABLE statement:ADD column MODIFY column DROP columnALTER TABLE tableADD (column datatype [DEFAULT expr][column datatype]….);ALTER TABLE tableMODIFY (column datatype [DEFAULT expr][column datatype]….);ALTER TABLE tableDROP (column datatype [DEFAULT expr][column datatype]….);
- 10. Table before add new column
- 11. Execute ALTER TABLE statement to ADD:
- 13. the ALTER TABLE
- 14. statement to ADDALTER TABLE emp ADD (job VARCHAR(9));
- 16. Table before MODIFY a column
- 17. Execute ALTER TABLE statement to MODIFY:
- 19. the ALTER TABLE
- 20. statement to
- 21. MODIFYALTER TABLE emp MODIFY (ename VARCHAR(3));
- 23. Table before DROP column
- 24. Execute ALTER TABLE statement to DROP:
- 26. the ALTER TABLE
- 27. statement to DROP:ALTER TABLE emp DROP COLUMN job;
- 28. Basic Structures in Query DesignQUERY WITH SQL
- 29. DEFINE THE INSTRUCTIONSELECT to query data in the databaseINSERT to insert data into a tableUPDATE to update data in a tableDELETE to delete data from a table
- 30. SELECT STATEMENTPurpose to retrieve and display data from one or more database tables.
- 31. It is an extremely powerful command capable of performing the equivalentof the relational algebra’s Selection, Projection and Join operations in a single statement.
- 32. It is most frequently used SQL command.
- 34. SELECT identifies what columns
- 35. FROM identifies which tableSELECT [DISTINCT] {*, column,…}FROM table;
- 36. SELECT STATEMENTSelect all columnsSelect specific columnsOutputSELECT * FROM dept;OutputSELECT Deptno, loc FROM dept;
- 37. SELECT STATEMENT Using WHERE clause.
- 39. The WHERE clause follows the FROM clauseSELECT [DISTINCT] {*, column,…}FROM tableWHERE condition(s);
- 40. SELECT STATEMENTUsing where clauseSelect specific columnsOutputSELECT ename, job, deptno FROM deptWHERE job = ‘CLERK’OutputSELECT Deptno, loc FROM deptWHERE loc = ‘New York’;
- 41. SELECT STATEMENTUsing BETWEEN operator to display rows based on a range of values OutputSELECT ename, sal FROM empWHERE sal BETWEEN 10000 AND 15000;
- 42. UPDATEUPDATE itemSET Quantity =10,UnitPrice =1800.00WHERE ItemNo = ‘123’;In this statement , only one row will be updated since the condition is specified in the WHERE clause, if the WHERE clause is omitted, all rows in the item table will be update.
- 43. DELETETo remove one or more rows from a table. For example , to delete the ItemNo = ‘123’.DELETEFROM itemWHERE ItemNo = ‘123’;
- 44. The syntax for inserting data into a table one row at a time is as follows: INSERT INTO "table_name" ("column1", "column2", ...)VALUES ("value1", "value2", ...)INSERT INTO
- 45. Assuming that we have a table that has the following structure :Table Store_InformationResult :INSERT INTO Store_Information (store_name, Sales, Date)VALUES (‘Ipoh', 900, 'Jan-10-1999')
- 46. The second type of INSERT INTO allows us to insert multiple rows into a table. Unlike the previous example, we now use a SELECT statement to specify the data that we want to insert into the table. The syntax is as follows: INSERT INTO "table1" ("column1", "column2", ...)SELECT "column3", "column4", ...FROM "table2"
- 47. Before using INSERT INTO commandTable Sales_InformationTable Store_InformationTable Sales_InformationTable Store_Information
- 48. After using INSERT INTO commandINSERT INTO Store_Information (store_name, Sales, Date)SELECT store_name, Sales, DateFROM Sales_InformationWHERE Year(Date) = 1998New information that been added to the tableTable Sales_InformationTable Store_Information
- 49. CREATE VIEWViews can be considered as virtual tables. Generally speaking, a table has a set of definition, and it physically stores the data. A view also has a set of definitions, which is build on top of table(s) or other view(s), and it does not physically store the data. The syntax for creating a view is as follows: CREATE VIEW "VIEW_NAME" AS "SQL Statement"
- 50. We have the following tableTABLE CustomerWe want to create a view called V_Customer that contains only the First_Name, Last_Name, and Country columns from this table, we would type in,CREATE VIEW V_CustomerAS SELECT First_Name, Last_Name, CountryFROM Customer
- 51. Now we have a view called V_Customer with the following structure: View V_Customer(First_Name char(50),Last_Name char(50),Country char(25))
- 52. We can also use a view to apply joins to two tables. In this case, users only see one view rather than two tables, and the SQL statement users need to issue becomes much simpler. Let's say we have the following two tablesTable Store_InformationTable Geography
- 53. We want to build a view that has sales by region informationCREATE VIEW V_REGION_SALESAS SELECT A1.region_name REGION, SUM(A2.Sales) SALESFROM Geography A1, Store_Information A2WHERE A1.store_name = A2.store_nameGROUP BY A1.region_nameThis gives us a view, V_REGION_SALES, that has been defined to store sales by region records.
- 54. SELECT * FROM V_REGION_SALES
- 55. Exercises:According to the table given, write SQL query for each of the following questions.Add a column called “TelNum” to this table.Change the column name for “Reg_Num” to “RegistrationNum”.Modify the data type of “Year_Born” to date.Delete the column “TelNum”.
- 56. TABLE CONSTRAINTS IN SQLNOT NULL
- 57. UNIQUE
- 58. PRIMARY KEY
- 59. FOREIGN KEYTABLE CONSTRAINTYou can place constraints to limit the type of data that can go into a table. Such constraints can be specified when the table when the table is first created via the CREATE TABLE statement, or after the table is already created via the ALTER TABLE statement.
- 60. 1) NOT NULLBy default, a column can hold NULL. If you not want to allow NULL value in a column, you will want to place a constraint on this column specifying that NULL is now not an allowable value.
- 61. Columns "SID" and "Last_Name" cannot include NULL, while "First_Name" can include NULL.Result :
- 62. 2) UNIQUEThe UNIQUE constraint ensures that all values in a column are distinct.“SID” column in customer table is modify so that "SID" column cannot include duplicate values, while such constraint does not hold for columns "Last_Name" and "First_Name".
- 63. Result :Indicates that “SID” column is unique
- 64. 3) PRIMARY KEYA primary key is used to uniquely identify each row in a table. It can either be part of the actual record itself , or it can be an artificial field. A primary key can consist of one or more fields on a table. When multiple fields are used as a primary key, they are called a composite key. Primary keys can be specified either when the table is created (using CREATE TABLE) or by changing the existing table structure (using ALTER TABLE).
- 65. Example :CREATE TABLE Customer (SID integer, Last_Name varchar(30), First_Name varchar(30), PRIMARY KEY (SID)); ALTER TABLE Customer ADD PRIMARY KEY (SID); Indicate that “SID” column has been choose to be the primary key.
- 67. 4) FOREIGN KEYA foreign key is a field (or fields) that points to the primary key of another table. The purpose of the foreign key is to ensure referential integrity of the data. In other words, only values that are supposed to appear in the database are permitted.
- 69. CREATE TABLE ORDERS (Order_ID integer, Order_Date date, Customer_SID integer, Amount double, Primary Key (Order_ID), Foreign Key (Customer_SID) references CUSTOMER(SID)); ALTER TABLE ORDERS ADD FOREIGN KEY (customer_sid) REFERENCES CUSTOMER(SID);Indicates the Customer_SID column in the ORDERS table is a foreign key pointing to the SID column in the CUSTOMER table