Download MYSQL Introduction MySQL A database that is available for no

MYSQL
Introduction
MySQL
A database that is available for no charge (open source) but with a commercial license
for those who want to use MySQL as part of a new software product and wants to sell the
new product. The developer would need to purchase a commercial license. The fee is very
reasonable.
Advantages:
 It’s fast. The main goal of the folks who developed MySQL was speed.
Consequently, the software was designed from the beginning with speed in mind.
 It’s inexpensive. MySQL is free under the open source GPL license, and the fee for a
commercial license is very reasonable.
 It’s easy to use. You can build and interact with a MySQL database by using a few
simple statements in the SQL language, which is the standard language for
communicating with RDBMSs.
 It can run on many operating systems. MySQL runs on a wide variety of operating
systems — Windows, Linux, Mac OS, most varieties of Unix (including Solaris, AIX,
and DEC Unix), FreeBSD, OS/2, Irix, and others.
 Technical support is widely available. A large base of users provides free support
via mailing lists. The MySQL developers also participate in the e-mail lists. You can
also purchase technical support from MySQL ABfor a very small fee.
 It’s secure. MySQL’s flexible system of authorization allows some or all database
privileges (for example, the privilege to create a database or delete data) to specific
users or groups of users. Passwords are encrypted.
 It supports large databases. MySQL handles databases up to 50 million rows or
more. The default file size limit for a table is 4GB, but you can increase this (if your
operating system can handle it) to a theoreticallimit of 8 million terabytes (TB).
 It’s customizable. The open source GPL license allows programmers to modify the
MySQL software to fit their own specific environments.
Load WampServer and get to phpMyAdmin link.
You will see an interface for creating MySQL database and table. Note that Home icon is very
valuable. What happens when clicked?
Creating database and table – or choosing them
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Create database or choose an existing one. To create, you type database name and create.
(Existing ones will be shown on the left column. You click to choose.)
Then create a table or choose an existing one. (Existing one will be shown on the left column
below a database when the database is chosen. You click to choose.)
When creating a table you give table name and specify number of fields. Then choose go.
You would see an interface for creating table structure. You specify field names, and type at least.
Next save the table.
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Working with tables
When the table is selected, then towards the top, you see several menus: Browse, structure, SQL,
Search, Insert, Export, Import, Operations and drop.
You use these as need be.
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Browse – for presenting records
Structure – for table structure. With this, you can set primary key, add a field (see menu at the
bottom), change or drop a field. (See heading action for these last two).
 SQL - for querying records etc and updating
 Insert - for adding records
 Operations- for performing actions such sorting.
 Drop – for deleting the table.
When you select a database, you see several menus towards the top. Included are privileges and drop.
Drop is for deleting a database. Privileges are for controlling access to the database. For this you will
add new user and grant privileges.
To add new user, you go through add new user. There you specify USER NAME, HOST AND
PASSWORDS. (You use these later when linking php application and the database, hence the table.)
Then on database user, grant privileges on the database and tick the privileges. If all are granted then
check all. This will be for the user only. Several database users could be there with varied privileges.
Export and import of tables
Export
 Export – to store in different place
 Go through phpMyAdmin
 Select database, then table and click export
 Under export, ensure SQL in text is selected then go.
 Choose save a file and select the location then save (if you cannot select location, save using
default one). A file by name, of the table with extension .sql will be saved in the location you
chose when saving.
 In case you used the default saving location, you now need to save or copy to medium of your
choice – say flash disk.
Import
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Now to get the file ready for import – the one you saved – if in flash disk, ensure you insert it
to your computer
 Go through phpMyAdmin
 Select database where the table will be then select import and browse to get to the .sql file you
had saved then open and go.
Field types
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There are several field types. Included are:
CHAR(length) Fixed-length character string.
VARCHAR(length) Variable-length character string. The longest string that can be stored is
length, which must be between 1 and 255.
TEXT Variable-length character string with a maximum length of 64KB of text.
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INT(length) Integer with a range from –2147483648 to +2147483647. The number that can
be displayed is limited by length. For example, if length is 4, only numbers from –999 to
9999 can be displayed, even though higher numbers are stored.
INT(length) UNSIGNED Integer with a range from 0 to 4294967295. length is the size of the
number that can be displayed. For example, if length is 4, only numbers up to 9999 can be
displayed, even though higher numbers are stored.
Generally you will use the following field types as you created tables:
 INT
 TEXT
 FLOAT
Privileges
Privileges are permissions.
Permission Description
 ALL- All permissions
 ALTER- Can alter the structure of tables
 CREATE -Can create new databases or tables
 DELETE -Can delete rows in tables
 DROP -Can drop databases or tables
 FILE -Can read and write files on the server
 GRANT -Can change the permissions on a MySQL account
 INSERT- Can insert new rows into tables
 SELECT -Can read data from tables
 SHUTDOWN -Can shut down the MySQL server
 UPDATE- Can change data in a table
 USAGE - No permissions at all
Granting ALL is not a good idea because it includes permissions for administrative operations, such
as shutting down the MySQL server.
SQL
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SQL (Structured Query Language) is the computer language that you use to communicate with
MySQL. SQL is almost English.
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The queries include:
o CREATE, DROP, ALTER, SHOW, INSERT, LOAD, SELECT, UPDATE, and
DELETE.
To show databases - SHOW DATABASES
You can delete any database with this SQL query:
o DROP DATABASE databasename
To see the tables that have been added to a database, use this SQL query:
o SHOW TABLES
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You can remove any table with this query:
o DROP TABLE tablename
Adding one row at a time
 You use the INSERT query to add a row to a database. This query tells MySQL which table to
add the row to and what the values are for the fields in the row. The general form of the query is:
INSERT INTO tablename ( ,....,columnname)
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VALUES (value, value,....,value)
columnname, columnname
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The following rules apply to the INSERT query:
o Values must be listed in the same order in which the column names are listed. The first value
in the value list is inserted into the column that’s named first in the column list; the second
value in the value list is inserted into the column that’s named second in the column list; and
so on.
o A partial column list is allowed. You don’t need to list all the columns. Columns that are not
listed are given their default value or left blank if no default value is defined.
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A column list is not required. If you’re entering values for all the columns, you don’t need to
list the columns at all. If no columns arelisted, MySQL will look for values for all the
columns, in the order in which they appear in the table.
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The column list and value list must be the same length.
If the list of columns is longer or shorter than the list of values, you get an error message like
this: Column count doesn’t match value count.
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The following INSERT query adds a row to the Member table:
INSERT INTO Member (loginName,createDate,password,lastName,
street,city,state,zip,email,phone,fax)
VALUES (“bigguy”,”2001-Dec-2”,”secret”,”Smith”,
“1234 Happy St”,”Las Vegas”,”NV”,”88888”,
“[email protected]”,”(555) 555-5555”,””)
Retrieving information
To retrieve specific information, list the columns containing the information you want. For
example:
o SELECT columnname,columnname,columnname,... FROM tablename
o This query retrieves the values from all the rows for the indicated column(s). For
instance, the following query retrieves all the last names and first names stored in the
Member table:
o SELECT lastName,firstName FROM Member
o You can perform mathematical operations on columns when you select them. For
example, you can use the following SELECT query to add two columns together:
o SELECT col1+col2 FROM tablename
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The simplest, basic SELECT query is
o SELECT * FROM tablename
You can sort in descending order by adding the word DESC before the column name.
For example:
SELECT * FROM Member ORDER BY DESC lastName
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This query retrieves all the last names stored in the table named Member. Of course, more
complicated queries (such as the following) are less English-like:
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SELECT lastName,firstName FROM Member WHERE state=”CA” AND city=”Fresno” ORDER
BY lastName
o This query retrieves all the last names and first names of members who live in Fresno
and then puts them in alphabetical order by last name.
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Or you could use the following query:
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SELECT price,price*1.08 FROM Pet
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The result is the price and the price with the sales tax of 8 percent added on.
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You can combine expressions ANDs and ORs. In some cases, you need to use parentheses to
clarify the selection criteria. For instance, you can use the following query to answer your boss’s
urgent need to find all the people in the Member Directory whose names begin with B, who live
in Santa Barbara, and who have an 8 in either their phone or fax number:
SELECT lastName,firstName FROM Member
WHERE lastName LIKE “B%”
AND city = “Santa Barbara”
AND (phone LIKE “%8%” OR fax LIKE “%8%”)
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Notice the parentheses in the last line. You would not get the results asked for without the
parentheses. Without the parentheses, each connector would be processed in order from the first
to the last, resulting in a list that includes all members whose names begin with B and who live in
Santa Barbara and whose phone numbers have an 8 in them and all members whose fax numbers
have an 8 in them, whether they live in Santa Barbara or not and whether their name begins with a
B or not. When the last OR is processed, members are selected whose characteristics match the
expression before the OR or the expression after the OR.
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LIMIT specifies how many rows can be returned. The form for LIMIT is LIMIT startnumber,
numberofrows
The first row that you want to retrieve is startnumber, and the number of rows that you want to
retrieve is numberofrows. If startnumber is not specified, 1 is assumed. To select only the first
three members who live in Texas, use this query:
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SELECT * FROM Member WHERE state=”TX” LIMIT 3
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Some SELECT queries will find identical records, but in this example, you only want to see one
— not all — of the identical records. To prevent the query from returning all the identical records,
add the word DISTINCT immediately after SELECT.
Updating information
 Changing information in an existing row is updating the information. For instance, you might
need to change the address of a member because she has moved, or you might need to add a fax
number that a member left blank when he originally entered his information. The UPDATE query
is very straightforward:
 UPDATE tablename SET column=value,column=value,...
WHERE clause
 In the SET clause, you list the columns to be updated and the new values to be inserted. List all
the columns that you want to change in one query. Without a WHERE clause, the values of the
column(s) would be changed in all the rows. But with the WHERE clause, you can specify which
rows to update. For instance, to update an address in the Member table, use this query:
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UPDATE Member SET street=”3333 Giant St”, phone=”555-555-5555” WHERE
loginName=”bigguy”
Removing information
 Keep the information in your database up to date by deleting obsolete information. You can
remove a row from a table with the DELETE query:
 DELETE FROM tablename WHERE clause
 Be extremely careful when using DELETE. If you use a DELETE query without a WHERE
clause, it will delete all the data in the table. The data cannot be recovered.
Creating relationships between tables
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Some tables in a database are related to one another. Most often, a row in one table is related to
several rows in another table. A column is needed to connect the related rows in different tables. In
many cases, you include a column in one table to hold data that matches data in the primary key
column of another table.
A common application that needs a database with two related tables is a customer order
application. For example, one table contains the customer information, such as name, address,
phone, and so on. Each customer can have from zero to many orders. You could store the order
information in the table with the customer information, but a completely new row would be created
each time that the customer placed an order, and each new row would contain the entire
customer’s information. It would be much more efficient to store the orders in a separate table. The
Order table would have a column that contains the primary key from a row in the Customer table so
that the order is related to the correct row of the Customer table.
How would you copy from one table to another?
Database containing tables should be selected. The command is:
use database_name
You could then refer to tables with the use of dots. Examples assuming the tables come from the
same database:
SELECT columnnamelist FROM table1,table2
WHERE table1.col2 = table2.col2
SELECT * FROM Pet,Color WHERE Pet.petName = Color.petName
How would you update? Could update command and the use of dot and comparison do? (SEARCH
THE NET AND REASON.)
Primary key
This is unique identifier of records. It must not have a null value. Values should not be repeated.
To make a field primary
While in structure menu with the right table open, click on the primary key icon against the field.
To change structure of table
By using the ALTER query, you can change the name of the table; add, drop, or rename a column; or
change the data type or other attributes of the column.
You can also change the table structure with the use of change icon against the field when in
structure menu. Then follow the process.
You can also delete a field with the use of drop icon against the field when in structure menu.
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To add a field, be on structure menu then check towards the bottom for items (or displays: add 1
field(s) ... at End of Table ... etc at then Go and act accordingly.
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