Database tables are basic entity to store data in oracle. It is a logical storage in oracle database.
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How employees table looks like in the database
The 1st row in the above image contains the column names of employees table. The columns are highlighted within the red square outline in the above example.
The green square section shows the number of rows or actual data in the table.
What did we know about database tables?
Every table has a unique name. We give this name when creating a table. Any table has one or more columns in it. It may or may not contain any data in it. Each column in a table has unique column name in the same table.
In the above diagram, we have 3 columns and 4 rows. Now, you might think that why I said 4 rows. The reason is, I talked about the actual data rows. The row mentioned with the help of a big red arrow is table meta information. It has column names in this case. The small red arrows signify actual data rows.
The green arrows show the number of columns the table has. In this case, we have 3 columns.
How to SELECT data from a table?
Oracle database contains one or more tables. Now the point is, how would you retrieve data from a table from a database having 100 tables. We do this with the help of Oracle SQL language.
To get data from a table, we write the following instruction or query.
SELECT * FROM <table name here>; --table name is unique to its parent
We wanted to get all the data from employees table. With the help of above query, oracle understands our motive. So the query would be s following.
SELECT * FROM employees;
Here, * means all the columns. We will talk more about this on SELECT query section.