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Salut to all! My name is T. Kalala living Claremont, Cape Town. I am regestered for DIT this january 20012 and currently studing the following modules: ICT13, ICT21, ICT31 and EUP1501
Chapter 7:Database Administration
08 Oct 2012
As in the network there are Server and Client extracting personal needed information from Server, it is that we call Views here Database as Server and Views as client with specific need that collected from Database trough defining query where lye all details of the particular required data to be retrieve from the base tables to make a personal table call View.
The View is very useful when the needs are of extracting Data from the Database and process them for output purpose but become very complex when the user require modification or change the same data, because the structure may come from different tables, that have different structure then the given View.
Grant and Revoke command are very important to limit the access of a given user of a particular Database base from their ability of understanding of database and consequence of their action. Special other user maybe not even be aware of there are using a table or view, then limiting witch command they may not use, are important to avoid commands like update, delete and drop because the irreparable consequence may derive from these commands.
Index here is shot representation of contains of data in database grouped from selected column as index key to speed the search in a database.
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Chapter 6: Updating Data
08 Oct 2012
Honestly from start until this chapter I never give much attention to the Autocommit check box at my big chock with the result after running rollback command that when I could realise my negligence and the importance the control state of Autocommit check box.
Creating a new table from an existing table is about how to transfer data from existing table to new created table. The use Insert, Update and how to combine the key to form the exact condition to execute the Query is capital special for update. Alter table with Add and Modify to add or modify existing column rely on definition and analyse of the type and size of data is necessary. Also the condition and demand to deal with null value and not null value when defining a column.
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Chapter 5: Multi tables Queries
08 Oct 2012
When exploring the multiple table Queries, end up asking myself why there are so much operators while 3 or 4 operators can be combine to rich the different outcome. After working on different exercises, using different operator combination I realize that certain operators have a shot Query to deliver the required outcome while other operator take a long query to the same outcome then I conclude that with experience each operator is set for a particular request for a quick result.
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Chapter 4: Single Table Query
27 Aug 2012
The major command in this chapter is Select that allow to view or to manipulate data of a table in SQL across the databases from Oracle, Access or SQL Server. We see the command select associate with clauses like Where or Having to specify the condition of display. The identification of the Simple condition most use only comparison operators and the Compound conditions or grouping conditions that used conditional operators and operators as:
– LIKE for wildcards when we don’t really remember the exact information of our key of search,
– IN operator to avoid a repetition of an operator in one Query to accurate the request.
– BETWEEN operator to declare a range of specific information needed.
Not only displaying but processing of information may also be done, Computed column generate after calculation with arithmetic operators can be assign a label with our own column title with AS and aggregate functions are in use, the use of Distinct operator is useful.
Sorting Order by clause, the syntax relay on the key search that can be simple or compounded with major and minor keys, the range of sorting need to be precise with Desc for descending or Asc for ascending. We can use ascending when presenting list students registered, candidates or products in store, and descending when displaying a list of students with High marks or percentages to the lows one or products with high demand to less demand.
The grouping of Data with the clause Group by the syntax of Query produce some complex syntax, my appreciation to the declaration of Subquery to simplify the complex Query. Also in this chapter I observe that SQL is more sensitive with the grammar of information of the row then with the syntax the command or commands.
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chapter 3: An Introductio to SQL
27 Aug 2012
I start this chapter already with question mark about what made SQL most popular and widely used the Database, was it the first language to be use for Database, as Microsoft was the first available PC Operation System or just more comfortable then other data retrieving and manipulation language?
I found that SQL still use the same command, syntax and structure in generally from Oracle, to Access or SQL Server not major change on how to write SQL command except when about the type of data oracle and SQL Server accept Decimal, access accept only currency or number; The insertion of Date in Oracle with single quote, while Access used the number sign and SQL Server using Datetime. It is also show that when writing the command the choice lower or up character and syntax is not major concern at some point, like writing semicolon at the end of the command may not stop the execution. I observed printing within Oracle is quiet simple then within Access.
Declaration of Not Null field is very important of some type of column, the use of SMALLINT in case when we know how many number will be contain on the field instead INT and the consideration of VARCHAR instead CHAR to avoid filling the Database with spaces.
I found the use of script file very important special to avoid waste of time on writing the same command with the same syntax again and again.
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Chapter two: Database design fundamentals
11 Aug 2012
Entity: is a grouping of information that related to define the group name, represent the figures in this course as table.
Attribute: is a define information gathered to form a named group, represent the figures in this course as column.
Relationship: is the way each group are connected with other groups or tables.
Relation: is when a set of defines information are selected what represent a row of table.
Relational database: is the collection of selected sets of defines information.
Functional dependence and identity when one column is functionally dependent on another is when a given information (column) allow to find or identify other unknown information (column), in those case the unknown information is functionally depended by the given one. The functional dependence cannot be declared just by looking at group (table) of information, but by reviewing the rules for entry of information in the table.
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Chapter one: Introduction database
11 Aug 2012
As human being from earlier age from Home structure with bedrooms, kitchen, bathrooms etc.; School structured with classrooms, offices, library etc.; we are exposed to some kind of structure or an organisation even our body itself is structured that every part have a place where it belong or to be find while interact with each other to respond to daily activities these are physical or visible object with a visible structure. While Database is not visible or physical, it is an electronically warehouse created to store a selected and grouped of information needed time to time for accomplishment of routine request, added or subtracted without modifying or changing their natures, types or categories of information and is structured to be accessible in many way, where the group are called table.
In this chapter we have 3 Database:
I interact with database on daily basic like when in Myunisa I to check academic record, financially statement or assignment marked and correction. I ordered a book from Masterskills all these are kind of using database from remote location.
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