Database Queries

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Select Commands

SELECT * from tableName
 - SELECT all columns FROM the table
SELECT column1, column2 FROM tableName
SELECT 2 columns FROM the tableName table
SELECT DISTINCT column FROM tableName
will display only unique results (no duplicates)
SELECT firstname || ' ' || lastname FROM tablename
will concatenate first and last name into one field (the ' ' between the || inserts a space)
SELECT fristname || ' ' || lastname "Customer Name" FROM table name
this will add a alias for the column heading called Customer Name
SELECT title AS "Title of Book", category FROM books;
This adds the column alias "Title of Book" to the results instead of using just the title as the column heading

select table_name FROM user_tables

that exact statement will list all tables

selecting column names, data type, and default values

select column_name, data_type, data_default from user_tab_columns where table_name = 'ACCTMANAGER'

Creating Calculated Fields in a Query

SELECT title, retail*cost as profit FROM books;
retail column is multiplied by cost and the result is displayed in the alias field profit

Using Concatenation

SELECT firstname || lastname FROM customers;
this will display the info but last and first names will be together eg. firstlast
to add a space between the names :
SELECT firstname || ' , ' | || lastname as "Customer Name" FROM customers;
this will add the , between the names and give it an alias heading "Customer name"

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