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EnterpriseDB: System Information
Oracle Tips by Burleson
 

CURRENT_DATABASE:  Return the current database name:

* Returns = VARCHAR2

CURRENT_USER:  Return the current executing user:

* Returns = VARCHAR2

SESSION_USER:  Return the current session user:

* Returns = VARCHAR2

VERSION:  Return the version of the database:

* Returns = VARCHAR2

SELECT CURRENT_DATABASE db,
       CURRENT_USER cu,
       SESSION_USER su,
       VERSION ver
FROM DUAL;

edb=# SELECT CURRENT_DATABASE db,
edb-#        CURRENT_USER cu,
edb-#        SESSION_USER su,
edb-#        VERSION ver
edb-# FROM DUAL;

 db  |      cu      |      su      |                    ver
-----+--------------+--------------+-------------------------------------------
 edb | enterprisedb | enterprisedb | EnterpriseDB 8.1.4.19 on i686-pc-linux-gnu

(1 row)

Conclusion

Well shiver me timbers!  This was an exciting chapter wasn't it?  We've learned just about everything that there is to know about a database.  Not quite, I guess.  This chapter won't make anyone a database guru but hopefully you feel confident in writing queries and creating database objects.

We went from comparing a filing cabinet to a database and a file folder to a table all the way through primary keys, foreign keys, unique constraints and just what NULL really means.  In our tour of database architecture, we took a quick look at an ERD and even discussed indexing and sequences. 

We followed that up with a detailed discussion of data types.  The following list is a reminder of the types we discussed:

* TEXT

* VARCHAR2

* CHAR

* CLOB

* NUMERIC

* NUMBER

* INTEGER

* BINARY_FLOAT and BINARY_DOUBLE

* OID

* Date and Time

* DATE and TIMESTAMP

* INTERVAL

* Binary Data

* RAW & BLOB

* BFILE

* Large Object

* Miscellaneous

* BOOLEAN

* Composite Type

* Arrays

After discussing data types, we went into a detailed discussion of the various object types in EnterpriseDB.  For each object type we discussed its CREATE, ALTER, GRANT, REVOKE and DROP commands.  From this discussion, you should have enough mastery over EnterpriseDB DDL to feel comfortable building most any application.

No discussion of SQL would be complete without a detailed description of the SELECT, INSERT, UPDATE, DELETE and other DML commands.  We discussed those and more and even ran through some pretty complex examples (remember that select from the inline view with the multiple unions?  Whew, that was a bear!).

And finally, we ended the chapter with a run through of the more common SQL functions and looked at some examples actually using them.  Don't bother memorizing syntax.  As long as you know the function exists, you can always look up the syntax.

The goal of this chapter was to give you a basic primer and give you the skills and knowledge to get you started.  I hope I accomplished that.  It's up to you to become a guru.

In the next chapter, we will dive deep into programming for EnterpriseDB.  We're going to delve deeply into the PL/SQL compatible, SPL language and we'll even briefly touch on some of the other EnterpriseDB supported languages like Perl and TCL.
 

             
This is an excerpt from the book "EnterpriseDB: The Definitive Reference" by Rampant TechPress.

  
 

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