Tag Archives: rules of sql

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Chapter 5 – Selecting Data From Multiple Tables Usage of multiple tables in one query Combining tables – JOIN Different Types of SQL Join Left Outer Join Right Outer Join …

Chapter 4 – Group Functions AVG Function SUM Function MIN Function MAX Function COUNT Function DISTINCT Function GROUP BY Statement HAVING Statement   One row functions can be applied to …

CONVERSION FUNCTIONS TO_CHAR (DATE) TO_CHAR(date, ‘format’) It’s case-sensitive and must be written between quotes. It must contain a valid date format. Let’s list the hire dates of employees like below. …

NUMERIC FUNCTIONS ROUND Let’s try some different usages of the ROUND function. SELECT ROUND (45.923), ROUND (45.943, 1), ROUND (45.924, 2), ROUND (44.923, -1), ROUND (55.923, -2) FROM DUAL;   …

Chapter 3 – Single Row Functions Charcter Functions Numeric Functions Date Functions Converting Functions NVL Function Decode Function CASE Statement   SQL FUNCTIONS SQL Functions can be classiifed under 2 …

OPERATOR PRECEDENCE   Let’s list the employees which JOB_ID is SA_REP or AD_PRES , and have salary more than 15000. SELECT first_name,last_name, job_id, salary FROM hr.employees WHERE job_id = 'SA_REP‘ …

IS NULL OPERATOR Let’s list the employees that have manager. SELECT first_name,last_name, manager_id FROM hr.employees WHERE manager_id IS not NULL;   LOGICAL OPERATORS AND : It returns TRUE if all …

CHAPTER 2 WHERE Conditions Comparison operators BETWEEN operator IN operator LIKE operator IS NULL operator Logical operators AND operator OR operator NOT operator ORDER BY operator   RESTRICTING ROWS WITH …

ARITHMETIC OPERATORS Arithmetic operations can be used on the data which type is ‘date’ or ‘number’. The priority of the operators is like below ;   USAGE OF THE ARITMETHIC …