SQL - Summaryhelix.biology.mcmaster.ca/2yy3/lecture9.pdf · SQL - Summary SHOW [ DATABASES j TABLES...

SQL - Summary

SHOW [ DATABASES | TABLES | COLUMNS FROM TableName ]SHOW [ CREATE [ DATABASE DBName | TABLE TableName ] ]SHOW [ STATUS | GRANTS | ERRORS | WARNINGS ]

SQL - Summary

SHOW [ ... ]

SELECT [ColName, ColName, ...] FROM [ TableName, TableName, ... ]

SQL - Summary

SHOW [ ... ]

SELECT [ColName, ColName, ...] FROM [ TableName, TableName, ... ]WHERE condition [logic condition ]

SQL - SELECT – ORDER BYCommands can be combined but order is important.

mysql> SELECT * FROM City WHERE ID < 20 ORDER BY CountryCode DESC, Name;

+----+-----------+-------------+---------------+------------+

| ID | Name | CountryCode | District | Population |

+----+-----------+-------------+---------------+------------+

| 17 | Almere | NLD | Flevoland | 142465 |

| 5 | Amsterdam | NLD | Noord-Holland | 731200 |

| 13 | Apeldoorn | NLD | Gelderland | 153491 |

| 18 | Arnhem | NLD | Gelderland | 138020 |

| 12 | Breda | NLD | Noord-Brabant | 160398 |

| 9 | Eindhoven | NLD | Noord-Brabant | 201843 |

| 15 | Enschede | NLD | Overijssel | 149544 |

| 11 | Groningen | NLD | Groningen | 172701 |

| 7 | Haag | NLD | Zuid-Holland | 440900 |

| 16 | Haarlem | NLD | Noord-Holland | 148772 |

...............

mysql> SELECT * FROM City ORDER BY CountryCode DESC, Name WHERE ID < 20;

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual

that corresponds to your MySQL server version for the right syntax to use

near ’WHERE ID < 20’ at line 1

SQL - Summary

SHOW [ ... ]

SELECT [ColName, ColName, ...] FROM [ TableName, TableName, ... ]WHERE condition [logic condition ]ORDER BY [ColName, ColName, ... ]

SQL - SELECT – LIMITToo much output can be controlled with LIMIT.

mysql> SELECT * FROM City LIMIT 15;

+----+----------------+-------------+---------------+------------+


+----+----------------+-------------+---------------+------------+

| 1 | Kabul | AFG | Kabol | 1780000 |

| 2 | Qandahar | AFG | Qandahar | 237500 |

| 3 | Herat | AFG | Herat | 186800 |

| 4 | Mazar-e-Sharif | AFG | Balkh | 127800 |

| 5 | Amsterdam | NLD | Noord-Holland | 731200 |

| 6 | Rotterdam | NLD | Zuid-Holland | 593321 |

| 7 | Haag | NLD | Zuid-Holland | 440900 |

| 8 | Utrecht | NLD | Utrecht | 234323 |

| 9 | Eindhoven | NLD | Noord-Brabant | 201843 |

| 10 | Tilburg | NLD | Noord-Brabant | 193238 |

| 11 | Groningen | NLD | Groningen | 172701 |

| 12 | Breda | NLD | Noord-Brabant | 160398 |

| 13 | Apeldoorn | NLD | Gelderland | 153491 |

| 14 | Nijmegen | NLD | Gelderland | 152463 |

| 15 | Enschede | NLD | Overijssel | 149544 |

+----+----------------+-------------+---------------+------------+

15 rows in set (0.07 sec)

SQL - SELECT – LIMITToo much output can be controlled with LIMIT.

mysql> SELECT * FROM City LIMIT 10 OFFSET 20;

+----+----------------+-------------+---------------+------------+


+----+----------------+-------------+---------------+------------+

| 21 | Amersfoort | NLD | Utrecht | 126270 |

| 22 | Maastricht | NLD | Limburg | 122087 |

| 23 | Dordrecht | NLD | Zuid-Holland | 119811 |

| 24 | Leiden | NLD | Zuid-Holland | 117196 |

| 25 | Haarlemmermeer | NLD | Noord-Holland | 110722 |

| 26 | Zoetermeer | NLD | Zuid-Holland | 110214 |

| 27 | Emmen | NLD | Drenthe | 105853 |

| 28 | Zwolle | NLD | Overijssel | 105819 |

| 29 | Ede | NLD | Gelderland | 101574 |

| 30 | Delft | NLD | Zuid-Holland | 95268 |

+----+----------------+-------------+---------------+------------+


mysql>

SQL - SELECT – LIMIT... or ... what I find confusing ...

mysql> SELECT * FROM City LIMIT 20,10;

+----+----------------+-------------+---------------+------------+


+----+----------------+-------------+---------------+------------+

| 21 | Amersfoort | NLD | Utrecht | 126270 |

| 22 | Maastricht | NLD | Limburg | 122087 |

| 23 | Dordrecht | NLD | Zuid-Holland | 119811 |

| 24 | Leiden | NLD | Zuid-Holland | 117196 |

| 25 | Haarlemmermeer | NLD | Noord-Holland | 110722 |

| 26 | Zoetermeer | NLD | Zuid-Holland | 110214 |

| 27 | Emmen | NLD | Drenthe | 105853 |

| 28 | Zwolle | NLD | Overijssel | 105819 |

| 29 | Ede | NLD | Gelderland | 101574 |

| 30 | Delft | NLD | Zuid-Holland | 95268 |

+----+----------------+-------------+---------------+------------+


mysql>

SQL - SELECT – LIMIT

All combined

mysql> SELECT * FROM City WHERE CountryCode="USA"

-> ORDER BY Population DESC LIMIT 5;

+------+--------------+-------------+--------------+------------+


+------+--------------+-------------+--------------+------------+

| 3793 | New York | USA | New York | 8008278 |

| 3794 | Los Angeles | USA | California | 3694820 |

| 3795 | Chicago | USA | Illinois | 2896016 |

| 3796 | Houston | USA | Texas | 1953631 |

| 3797 | Philadelphia | USA | Pennsylvania | 1517550 |

+------+--------------+-------------+--------------+------------+


mysql>

SQL - Summary

SHOW [ ... ]

SELECT [ColName, ColName, ...] FROM [ TableName, TableName, ... ]WHERE condition [logic condition ]ORDER BY ColName [, ColName, ... ]LIMIT number

SQL - PatternsSQL provides a wildcard in the form of ‘%’. This will match zeroor more characters. A less commonly used wildcard is ‘ ’ whichmatches one (and only one) character (zero characters is not amatch).

mysql> SELECT Name, District FROM City

-> WHERE Name LIKE ’%cate%’;

+---------------------+-----------+

| Name | District |

+---------------------+-----------+

| Zacatecas | Zacatecas |

| Ecatepec de Morelos | Mexico |

+---------------------+-----------+

but


-> WHERE Name LIKE ’_cate%’;

+---------------------+-----------+

| Name | District |

+---------------------+-----------+


+---------------------+-----------+

SQL - Patterns

To match a more general pattern, SQL permits regular expressions.


-> WHERE Name REGEXP ’cate’;

+---------------------+-----------+

| Name | District |

+---------------------+-----------+

| Zacatecas | Zacatecas |


+---------------------+-----------+


-> WHERE Name LIKE ’cate’;

Empty set (0.00 sec)

SQL - Patterns

mysql> SELECT Name, District FROM City-> WHERE Name REGEXP ’cate|kate’;

+---------------------+------------+| Name | District |+---------------------+------------+| Zacatecas | Zacatecas || Jekaterinburg | Sverdlovsk || Ecatepec de Morelos | Mexico |+---------------------+------------+3 rows in set (0.00 sec)

SQL - Patterns

mysql> SELECT Name, District FROM City-> WHERE Name REGEXP ’.[c-k]ate’;

+---------------------------+---------------+| Name | District |+---------------------------+---------------+| Zacatecas | Zacatecas || Farrukhabad-cum-Fatehgarh | Uttar Pradesh || Hakodate | Hokkaido || Jekaterinburg | Sverdlovsk || Ecatepec de Morelos | Mexico |+---------------------------+---------------+

SQL - Patterns


-> WHERE Name REGEXP ’.[^c-k]ate’;

+---------------------+------------------+

| Name | District |

+---------------------+------------------+

| San Mateo | California |

| Clearwater | Florida |

| Klaten | Central Java |

| San Mateo | Southern Tagalog |

| Berazategui | Buenos Aires |

| Ciudad de Guatemala | Guatemala |

+---------------------+------------------+


SQL - Patterns


-> WHERE Name REGEXP ’[^c-k]ate’;

+---------------------+------------------+

| Name | District |

+---------------------+------------------+

| San Mateo | California |

| Clearwater | Florida |

| Klaten | Central Java |

| Waterbury | Connecticut |

| San Mateo | Southern Tagalog |

| Paterson | New Jersey |

| Pate | Taoyuan |

| Berazategui | Buenos Aires |

| Ciudad de Guatemala | Guatemala |

+---------------------+------------------+


SQL - Patternsmysql> SELECT Name, Population FROM City

-> WHERE Population REGEXP ’1{4,6}’;

+----------------+------------+

| Name | Population |

+----------------+------------+

| Sergijev Posad | 111100 |

+----------------+------------+

1 row in set (0.00 sec)

mysql> SELECT Name, Population FROM City

-> WHERE Population REGEXP ’2{4,6}’;

+------------+------------+

| Name | Population |

+------------+------------+

| Rio Grande | 182222 |

| Chalco | 222201 |

| Embu | 222223 |

| Oradea | 222239 |

+------------+------------+


SQL - Patterns

For regular expressions, the statement

{n,m} means at least n to m matches{n,} means at least n{n} means exactely n+ means one or more, {1,}* means zero or more

(each of the above appliesto the previous character)

^ anchor to the line beginning$ anchor to the end of line

SQL - Patterns

Regular expressions can also match the unmatchable ...

simply put a double slash in front of the unmatchable.

For example, ‘\\.’ will match an actual period rather than anycharacter. ‘\\^’ will match a caret while ‘\\t’ will match atab.

SQL - Patterns

You can match patterns within a list of things usingIN (a comma separated list)

or alternativelyNOT IN (a comma separated list)

mysql> SELECT * FROM City WHERE Name IN (’Ottawa’,

-> ’Toronto’, ’Guelph’);

+------+----------+-------------+----------+------------+


+------+----------+-------------+----------+------------+

| 1850 | Guelph | CAN | Ontario | 103593 |

| 1822 | Ottawa | CAN | Ontario | 335277 |

| 1812 | Toronto | CAN | Ontario | 688275 |

+------+----------+-------------+----------+------------+


mysql> SELECT * FROM City WHERE (Name NOT IN (’Ottawa’,

-> ’Toronto’, ’Guelph’) AND District = ’Ontario’);

SQL - Patterns

You can match patterns within a range usingBETWEEN x AND y

One can also do “full text matching” but that is beyond thescope of this course.

SQL - JOINCombining information from different tables.

mysql> SELECT District, Language FROM City JOIN

-> CountryLanguage USING(CountryCode) LIMIT 10;

+----------+------------+

| District | Language |

+----------+------------+

| Kabol | Balochi |

| Kabol | Dari |

| Kabol | Pashto |

| Kabol | Turkmenian |

| Kabol | Uzbek |

| Qandahar | Balochi |

| Qandahar | Dari |

| Qandahar | Pashto |

| Qandahar | Turkmenian |

| Qandahar | Uzbek |

+----------+------------+


mysql>

SQL - JOIN

This comes from ...

mysql> SELECT District,

-> CountryCode FROM City;

+---------------+-------------+

| District | CountryCode |

+---------------+-------------+

| Kabol | AFG |

| Qandahar | AFG |

| Herat | AFG |

| Balkh | AFG |

| Noord-Holland | NLD |

...............

mysql>

mysql> SELECT Language, CountryCode

-> FROM CountryLanguage;

+------------+-------------+

| Language | CountryCode |

+------------+-------------+

| Dutch | ABW |

| English | ABW |

| Papiamento | ABW |

| Spanish | ABW |

| Balochi | AFG |

...............

mysql>

SQL - JOIN

Joins – Combining data from multiple tables.

The exact way in which the JOIN is done can vary (more on this later).

It works only when two tables share a column with the same name (thereis a different way to combine info from tables without this condition).

With the exception of this column (identified by USING) the columnnames must be unambiguous. To specify names that may not beunambiguous use TABLE NAME . COLUMN NAME.

You can join information from more than one column byUSING(column 1, column 2).

WARNING: if you leave off the USING statement you will not get an error

but nor do you get a JOIN. Instead you get a Cartesian product of the

tables.

SQL - Summary

SHOW [ ... ]SELECT [ColName, ColName, ...] FROM [ TableName, TableName, ... ]

WHERE condition [logic condition ]ORDER BY ColName [, ColName, ... ]LIMIT number

SELECT ColName, ColName, ... FROM TableNameJOIN TableName USING(..)

SQL - one of INSERTs

We can add individual data sets to tables. This is usually donethrough a browser so that the database operator does not do thiswork. But you must know it to program it and you must know theproblems.

mysql> SELECT * FROM City WHERE Name="Dundas";

Empty set (0.00 sec)

mysql> SELECT * FROM City WHERE Name="Grimsby";

+-----+---------+-------------+----------+------------+


+-----+---------+-------------+----------+------------+

| 534 | Grimsby | GBR | England | 89000 |

+-----+---------+-------------+----------+------------+


mysql>

SQL - one of INSERTsSo lets add them to the database.

mysql> DESC City;

+-------------+----------+------+-----+---------+----------------+

| Field | Type | Null | Key | Default | Extra |

+-------------+----------+------+-----+---------+----------------+

| ID | int(11) | | PRI | NULL | auto_increment |

| Name | char(35) | | | | |

| CountryCode | char(3) | | | | |

| District | char(20) | | | | |

| Population | int(11) | | | 0 | |

+-------------+----------+------+-----+---------+----------------+


mysql> INSERT INTO City VALUES (NULL, "Dundas", "CAN", "Ontario", 21000);

Query OK, 1 row affected (0.50 sec)

mysql> SELECT * FROM City WHERE Name="Dundas";

+------+--------+-------------+----------+------------+


+------+--------+-------------+----------+------------+

| 4080 | Dundas | CAN | Ontario | 21000 |

+------+--------+-------------+----------+------------+


mysql>


To add Grimsby ...

mysql> INSERT INTO City VALUES (NULL, "Grimsby", "CAN", "Ontario", NULL);

ERROR 1048 (23000): Column ’Population’ cannot be null

mysql> INSERT INTO City VALUES (NULL, "Grimsby", "CAN", "Ontario");

ERROR 1136 (21S01): Column count doesn’t match value count at row 1

mysql> INSERT INTO City VALUES (NULL, "Grimsby", "CAN", "Ontario", 0);


mysql> SELECT * FROM City WHERE Name="Dundas" OR Name="Grimsby";

+------+---------+-------------+----------+------------+


+------+---------+-------------+----------+------------+

| 534 | Grimsby | GBR | England | 89000 |


| 4081 | Grimsby | CAN | Ontario | 0 |

+------+---------+-------------+----------+------------+


mysql>


... but ...

mysql> INSERT INTO City VALUES (NULL, "Ancaster",

-> "CAN", "Ontario", DEFAULT);


mysql> SELECT * FROM City WHERE ID >= 4080;

+------+----------+-------------+----------+------------+


+------+----------+-------------+----------+------------+


| 4081 | Grimsby | CAN | Ontario | 0 |

| 4082 | Ancaster | CAN | Ontario | 0 |

+------+----------+-------------+----------+------------+


mysql>


These can done all at once.

mysql> INSERT INTO City VALUES

-> (NULL, "Dundas", "CAN", "Ontario", 21000),

-> (NULL, "Grimsby", "CAN", "Ontario", 0);

Query OK, 2 rows affected (0.50 sec)

mysql>


An alternate syntax would be ...

mysql> INSERT INTO City (Name, Population, Region, Country) VALUES

-> (NULL, "Dundas", "CAN", "Ontario", 21000),

-> (NULL, "Grimsby", "CAN", "Ontario", 0);


mysql>

Or if you needed to add only one entry ...

mysql> INSERT INTO City SET Name = "Dundas", Population = 21000,

-> Region ="Ontario", Country = "CAN";


mysql>

SQL - Summary



SELECT ColName, ColName, ... FROM TableName JOIN TableName USING(..)

INSERT INTO TableName VALUES (.., .., ..), (), ()INSERT INTO TableName (ColName, ColName, ...) VALUES (.., .., ..), (), ()INSERT INTO TableName SET ColName=.., ColName=.., ...

SQL - DELETE

To delete ...

mysql> DELETE FROM City WHERE ID >= 4080;


mysql>

DELETE will remove rows from a table. If thereis no WHERE or LIMIT clause it will happily re-move all rows (but will not delete the table).

SQL - UPDATE

To change just a value of a column ...

mysql> UPDATE City SET Population = "24000" WHERE Name ="Grimsby";


Rows matched: 2 Changed: 2 Warnings: 0

mysql>

Hmmmm, ... there is something wrong here ... canyou spot it?

SQL - UPDATE

So what about error management?

Well MySQL has NONE ! So rules for both UPDATE and DELETE.

1. Never execute without a WHERE or LIMIT clause.

2. Use the primary key in your WHERE clause.

3. Test your selection with a SELECT statement before execution.

4. Use enforced referential integrity to ensure data required inother tables is not affected.

There is no UNDO button†

† Not strictly true ... transactions can be ROLLBACK’ed to the start of a transaction... more on this later.

SQL - Summary



SELECT ColName, ColName, ... FROM TableName JOIN TableName USING(..)INSERT INTO TableName VALUES (.., .., ..), (), ()INSERT INTO TableName (ColName, ColName, ...) VALUES (.., .., ..), (), ()INSERT INTO TableName SET ColName=.., ColName=.., ...

DELETE FROM TableName [WHERE ... | LIMIT .. ]UPDATE TableName SET ColName=.. [WHERE ... | LIMIT .. ]

SQL - Creation

To create a new database ...

mysql> CREATE DATABASE species;


mysql> USE species;

Database changed

mysql> CREATE DATABASE species;

ERROR 1007 (HY000): Can’t create database ’species’; database exists

mysql> CREATE DATABASE IF NOT EXISTS species;


mysql>

SQL - CreationTo create a new database ...

mysql> CREATE TABLE sample (

-> sample_id SMALLINT(10) NOT NULL AUTO_INCREMENT,

-> date_collected TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,

-> collection_site_id SMALLINT(10) DEFAULT NULL,

-> sample_description TEXT DEFAULT NULL,

-> PRIMARY KEY(sample_id) );


mysql> DESC sample;

+--------------------+--------------+------+-----+-------------------+----------------+

| Field | Type | Null | Key | Default | Extra |

+--------------------+--------------+------+-----+-------------------+----------------+

| sample_id | smallint(10) | | PRI | NULL | auto_increment |

| date_collected | timestamp | YES | | CURRENT_TIMESTAMP | |

| collection_site_id | smallint(10) | YES | | NULL | |

| sample_description | text | YES | | NULL | |

+--------------------+--------------+------+-----+-------------------+----------------+


mysql> INSERT INTO sample VALUE (NULL, NULL, 1, "Some suitably slimmy thingy");


mysql> SELECT * FROM sample;

+-----------+---------------------+--------------------+-----------------------------+

| sample_id | date_collected | collection_site_id | sample_description |

+-----------+---------------------+--------------------+-----------------------------+

| 1 | 2009-01-25 14:50:08 | 1 | Some suitably slimmy thingy |

+-----------+---------------------+--------------------+-----------------------------+


mysql>

SQL - Creation

To create a new database ...

mysql> SHOW CREATE TABLE sample;

+--------+------------------------------------------------------+

| Table | Create Table |

+--------+------------------------------------------------------+

| sample | CREATE TABLE ‘sample‘ (

‘sample_id‘ smallint(10) NOT NULL auto_increment,

‘date_collected‘ timestamp NOT NULL default CURRENT_TIMESTAMP,

‘collection_site_id‘ smallint(10) default NULL,

‘sample_description‘ text,

PRIMARY KEY (‘sample_id‘)

) ENGINE=MyISAM DEFAULT CHARSET=latin1 |

+--------+------------------------------------------------------+


mysql> SHOW CHARSET;

+----------+-----------------------------+---------------------+--------+

| Charset | Description | Default collation | Maxlen |

+----------+-----------------------------+---------------------+--------+

| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |

| dec8 | DEC West European | dec8_swedish_ci | 1 |

| cp850 | DOS West European | cp850_general_ci | 1 |

..................

SQL - Creation

Note that table names

I are case sensitive in UNIX and Mac-OSX

I are limited to 64 characters

I should not contain MySQL reserved words (SELECT, etc.)

I cannot contain reserved characters (e.g. ‘/’).

Note that column names are NOT case sensitive even in UNIX andMac-OSX.

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SQL - Summaryhelix.biology.mcmaster.ca/2yy3/lecture9.pdf · SQL - Summary SHOW [ DATABASES j TABLES...

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