Step 0 How to begin and what you need to do before you start?

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1 Written and cooked by Janusz R. Getta, School of Computing and Information Technology, University of Wollongong Building 3, room 2120, ext 4339, jrg ËÁ̽½ Ø Å Ò Ñ ÒØ Ò Ë ÙÖ ØÝ Ê Ô º ÀÓÛ ØÓ Ø Ø ÓÒ ÖÝ Table of contents Step 0 How to begin and what you need to do before you start? Step 1 How to find what relational tables implement a data dictionary? Step 2 How to find information about relational tables? Step 3 How to find information about relational views? Step 0 How to begin and what you need to do before you start? A printable copy of this experiment in pdf format is available here ( e8-3.pdf). Logon to your Win 7 system and start VirtualBox. Next, either import your appliance from your USB drive and start imported virtual machine or use one of the brand new virtual machines available on your Win 7 system. Logon to Ubuntu operating system as CSIT115 user. Start Terminal application. In this experiment we use command line interface to communicate with mysql database server. Next, start start a command based interface to MySQL database server and to logon as a user csit115. Use a database csit115 and if you have not created a relational table Q in the previous experiment then do it now. USE csit115; CREATE TABLE Q(A CHAR(5)); Next, create a relational view in the following way. CREATE VIEW V AS (SELECT * FROM Q WHERE A = ); In every database system a data dictionary contains information about all databases created by the users, relational tables, relational views, indices, privileges granted to database users,... etc. It is so called metadata information. Typically such information is kept in one of the databases controlled by a database system. In MySQL a database called as information_schema contans all metadata of the system. As in the other database systems information_schema is a collection of relational tables. Find, the names of database available to csit115 user. SHOW DATABASES; A user csit115 has access to the following databases Database information_schema csit115 1

2 Make information_schema the current database of a user csit115. USE information_schema; Step 1 How to find the names of relational tables that implement a data dictionary? To find the names of relational tables implementing a data dictionary process the following statement. SHOW TABLES; The system should reply with the names of the following tables Tables_in_information_schema CHARACTER_SETS COLLATIONS COLLATION_CHARACTER_SET_APPLICABILITY COLUMNS COLUMN_PRIVILEGES ENGINES EVENTS FILES GLOBAL_STATUS GLOBAL_VARIABLES KEY_COLUMN_USAGE OPTIMIZER_TRACE PARAMETERS PARTITIONS PLUGINS PROCESSLIST PROFILING REFERENTIAL_CONSTRAINTS ROUTINES SCHEMATA SCHEMA_PRIVILEGES SESSION_STATUS SESSION_VARIABLES STATISTICS TABLES TABLESPACES TABLE_CONSTRAINTS TABLE_PRIVILEGES TRIGGERS USER_PRIVILEGES VIEWS INNODB_LOCKS INNODB_TRX INNODB_SYS_DATAFILES INNODB_FT_CONFIG INNODB_SYS_VIRTUAL 2

3 INNODB_CMP INNODB_FT_BEING_DELETED INNODB_CMP_RESET INNODB_CMP_PER_INDEX INNODB_CMPMEM_RESET INNODB_FT_DELETED INNODB_BUFFER_PAGE_LRU INNODB_LOCK_WAITS INNODB_TEMP_TABLE_INFO INNODB_SYS_INDEXES INNODB_SYS_TABLES INNODB_SYS_FIELDS INNODB_CMP_PER_INDEX_RESET INNODB_BUFFER_PAGE INNODB_FT_DEFAULT_STOPWORD INNODB_FT_INDEX_TABLE INNODB_FT_INDEX_CACHE INNODB_SYS_TABLESPACES INNODB_METRICS INNODB_SYS_FOREIGN_COLS INNODB_CMPMEM INNODB_BUFFER_POOL_STATS INNODB_SYS_COLUMNS INNODB_SYS_FOREIGN INNODB_SYS_TABLESTATS rows in set (0.00 sec) Step 2 How to find information about relational tables? Information about all relational tables created by the users is included in a relational table TABLES located in information_schema database. Execute a statement DESCRIBE to find the names of columns in a relational table TABLES. DESCRIBE TABLES; Field Type Null Key Default Extra TABLE_CATALOG varchar(512) NO TABLE_SCHEMA varchar(64) NO TABLE_NAME varchar(64) NO TABLE_TYPE varchar(64) NO ENGINE varchar(64) YES NULL VERSION bigint(21) unsigned YES NULL ROW_FORMAT varchar(10) YES NULL TABLE_ROWS bigint(21) unsigned YES NULL AVG_ROW_LENGTH bigint(21) unsigned YES NULL DATA_LENGTH bigint(21) unsigned YES NULL MAX_DATA_LENGTH bigint(21) unsigned YES NULL 3

4 INDEX_LENGTH bigint(21) unsigned YES NULL DATA_FREE bigint(21) unsigned YES NULL AUTO_INCREMENT bigint(21) unsigned YES NULL CREATE_TIME datetime YES NULL UPDATE_TIME datetime YES NULL CHECK_TIME datetime YES NULL TABLE_COLLATION varchar(32) YES NULL CHECKSUM bigint(21) unsigned YES NULL CREATE_OPTIONS varchar(255) YES NULL TABLE_COMMENT varchar(2048) NO The contents of a data dictionary table TABLES can be search with SELECT statement in the following way. SELECT TABLE_NAME, TABLE_TYPE FROM TABLES; TABLE_NAME TABLE_TYPE CHARACTER_SETS SYSTEM VIEW COLLATIONS SYSTEM VIEW COLLATION_CHARACTER_SET_APPLICABILITY SYSTEM VIEW COLUMNS SYSTEM VIEW COLUMN_PRIVILEGES SYSTEM VIEW ENGINES SYSTEM VIEW EVENTS SYSTEM VIEW FILES SYSTEM VIEW GLOBAL_STATUS SYSTEM VIEW GLOBAL_VARIABLES SYSTEM VIEW KEY_COLUMN_USAGE SYSTEM VIEW OPTIMIZER_TRACE SYSTEM VIEW PARAMETERS SYSTEM VIEW PARTITIONS SYSTEM VIEW PLUGINS SYSTEM VIEW PROCESSLIST SYSTEM VIEW PROFILING SYSTEM VIEW REFERENTIAL_CONSTRAINTS SYSTEM VIEW ROUTINES SYSTEM VIEW SCHEMATA SYSTEM VIEW SCHEMA_PRIVILEGES SYSTEM VIEW SESSION_STATUS SYSTEM VIEW SESSION_VARIABLES SYSTEM VIEW STATISTICS SYSTEM VIEW TABLES SYSTEM VIEW TABLESPACES SYSTEM VIEW TABLE_CONSTRAINTS SYSTEM VIEW TABLE_PRIVILEGES SYSTEM VIEW TRIGGERS SYSTEM VIEW USER_PRIVILEGES SYSTEM VIEW VIEWS SYSTEM VIEW 4

5 INNODB_LOCKS SYSTEM VIEW INNODB_TRX SYSTEM VIEW INNODB_SYS_DATAFILES SYSTEM VIEW INNODB_FT_CONFIG SYSTEM VIEW INNODB_SYS_VIRTUAL SYSTEM VIEW INNODB_CMP SYSTEM VIEW INNODB_FT_BEING_DELETED SYSTEM VIEW INNODB_CMP_RESET SYSTEM VIEW INNODB_CMP_PER_INDEX SYSTEM VIEW INNODB_CMPMEM_RESET SYSTEM VIEW INNODB_FT_DELETED SYSTEM VIEW INNODB_BUFFER_PAGE_LRU SYSTEM VIEW INNODB_LOCK_WAITS SYSTEM VIEW INNODB_TEMP_TABLE_INFO SYSTEM VIEW INNODB_SYS_INDEXES SYSTEM VIEW INNODB_SYS_TABLES SYSTEM VIEW INNODB_SYS_FIELDS SYSTEM VIEW INNODB_CMP_PER_INDEX_RESET SYSTEM VIEW INNODB_BUFFER_PAGE SYSTEM VIEW INNODB_FT_DEFAULT_STOPWORD SYSTEM VIEW INNODB_FT_INDEX_TABLE SYSTEM VIEW INNODB_FT_INDEX_CACHE SYSTEM VIEW INNODB_SYS_TABLESPACES SYSTEM VIEW INNODB_METRICS SYSTEM VIEW INNODB_SYS_FOREIGN_COLS SYSTEM VIEW INNODB_CMPMEM SYSTEM VIEW INNODB_BUFFER_POOL_STATS SYSTEM VIEW INNODB_SYS_COLUMNS SYSTEM VIEW INNODB_SYS_FOREIGN SYSTEM VIEW INNODB_SYS_TABLESTATS SYSTEM VIEW Q BASE TABLE Note a name of a relational table Q already created in a database csit115. Also note, that in fact a data dictionary does not consists of relational tables but SYSTEM VIEWs. This is because data dictionary tables do not really exist in the database systems and are simulated by software. Next, we try to find the names and types of the columns in a given relational table. To do so, we first investigate a structure of COLUMNS system view. DESCRIBE COLUMNS; Field Type Null Key Default Extra TABLE_CATALOG varchar(512) NO TABLE_SCHEMA varchar(64) NO TABLE_NAME varchar(64) NO COLUMN_NAME varchar(64) NO ORDINAL_POSITION bigint(21) unsigned NO 0 COLUMN_DEFAULT longtext YES NULL 5

6 IS_NULLABLE varchar(3) NO DATA_TYPE varchar(64) NO CHARACTER_MAXIMUM_LENGTH bigint(21) unsigned YES NULL CHARACTER_OCTET_LENGTH bigint(21) unsigned YES NULL NUMERIC_PRECISION bigint(21) unsigned YES NULL NUMERIC_SCALE bigint(21) unsigned YES NULL DATETIME_PRECISION bigint(21) unsigned YES NULL CHARACTER_SET_NAME varchar(32) YES NULL COLLATION_NAME varchar(32) YES NULL COLUMN_TYPE longtext NO NULL COLUMN_KEY varchar(3) NO EXTRA varchar(30) NO PRIVILEGES varchar(80) NO COLUMN_COMMENT varchar(1024) NO GENERATION_EXPRESSION longtext NO NULL rows in set (0.00 sec) Next we retrieve from data dictionary information about table name, column names, and types of a relational table Q. SELECT TABLE_NAME, COLUMN_NAME, COLUMN_TYPE FROM COLUMNS WHERE TABLE_NAME= Q ; TABLE_NAME COLUMN_NAME COLUMN_TYPE Q A char(5) row in set (0.00 sec) Step 3 How to find information about relational views? Ceate a relational view V in the following way. CREATE VIEW V AS (SELECT * FROM Q WHERE A = ); Next, retrieve from data dictionary information about all views. SELECT TABLE_NAME, VIEW_DEFINITION FROM VIEWS; TABLE_NAME VIEW_DEFINITION V (select csit115. Q. A AS A from csit115. Q where ( csit115. Q. A = )) 6

7 row in set (0.00 sec) References MySQL 5.7 Reference Manual, Chapter 23 INFORMATION SCHEMA Tables ( MySQL 5.7 Reference Manual, SELECT statement ( MySQL 5.7 Reference Manual, CREATE VIEW Statement ( 7