![Select statement
Used to “read”data from the database
**No changes are being made to the data
Select [* | column_list ]
From <table_name>
Where <filter_conditions>
Group by <group columns>
Having <filters on groups>
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Oracle SQL - Select Part -1 let's write some queries!
- 1. 3. Select part-1 : Getting started • Revisit connections and scripts • First Select ( and what is a table?! ) • All columns or some columns • Data Types • Aliases • Primary keys http://adata.guru
- 2. Running scripts SQL*Plus: @”..full_path../my_query.sql” SQL Developer SQLFiddle http://adata.guru
- 3. What is a table? One of the basic database object types http://adata.guru 14 Rows 8 Columns
- 4. Select statement Used to “read”data from the database **No changes are being made to the data Select [* | column_list ] From <table_name> Where <filter_conditions> Group by <group columns> Having <filters on groups> http://adata.guru
- 5. Wild card v/s columns http://adata.guru * all columns Specific columns Structure (shift+f4)
- 6. Data types Describe what kind of data a column has. http://adata.guru Column Name Datatype (length/precision)
- 7. List of Oracle Data types http://docs.oracle.com/cd/B28359_01/server.111/b28318/datatype.htm#i16209 • Character – char (fixed length string) eg. Char(10) – “Hello “ – varchar2( variable length string) eg. Varchar2(10) – “Hello” – and more… • Numeric – Number. Eg 123.50 – and more.. • Date – Date eg. 15-aug-1947 00:02:00 AM (includes time component) – Timestamp eg. 15-aug-1947 00:02:00.155 AM • and more… http://adata.guru
- 8. Primary Key • Uniquely identifies the row in a table. Check the constraints section in the table definition. http://adata.guru Use SHIFT+F4 shortcut key for SQL Developer and F4 if you are using Toad.
- 9. (column) Aliases • More readable, meaningful and useful column headers. • Very useful when dealing with complex names or generating reports http://adata.guru
- 10. (column) Aliases • Useful when you want contextual and meaningful names This kind of join is called a self-join where we join a table (emp) with itself. We’ll cover this in more detail in the JOINS Chapter. http://adata.guru Same column different heading based on context/meaning
- 11. Unlocking other schemas List of user account present in the database Conn / as sysdba Select username from dba_users Demo Accounts : http://docs.oracle.com/cd/E11882_01/server.112/e10831/installation.htm Unlocking acccounts: Conn / as sysdba Alter user hr identified by “hr”; Alter user oe identified by “oe”; Alter user pm identified by “pm”; Alter user sh identified by “sh”; Alter user ix identified by “ix”; http://adata.guru