Deep Dive - till operator precedence

Author: ptyadana

Diff for: Complete SQL & Databases - ZTM/05_SQL_Deep_Dive.sql

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+/************ 2) Simple Exercises *********/
+/* List all emmployees */
+SELECT * FROM employees LIMIT 10;
+
+/* How many departments? */
+SELECT COUNT(*) FROM departments;
+
+/* How many times has Employee 10001 has a raise? */
+SELECT COUNT(*) AS Number_of_raises FROM salaries
+WHERE emp_no = 10001;
+
+/* What title has 10006 has? */
+SELECT title FROM titles
+WHERE emp_no = 10006;
+
+/***************** 5) Column Concat *****************/
+SELECT CONCAT(emp_no, ' is  a ', title) AS "EmpTitle" FROM titles
+LIMIT 5;
+
+SELECT emp_no, 
+		CONCAT(first_name, ' ', last_name) AS "Full Name"
+FROM employees
+LIMIT 5;
+
+/************** 6) Types of Functions in SQL *************/
+/*
+Aggerate - operate on MANY records to produce ONE value, example: SUM of salaries
+Scalar - operate on EACH record Independently, example: CONCAT , it doesn't return result of concat values as one value.
+*/
+
+/*********** 7) Aggregate Functions ************/
+/*
+AVG()
+COUNT()
+MIN()
+MAX()
+SUM()
+*/
+SELECT COUNT(*) FROM employees;
+
+SELECT MIN(emp_no) FROM employees;
+
+/* Get the highest salary avaliable */
+SELECT MAX(salary) AS Max_Salary FROM salaries;
+
+/* Get the total amount of salaries paid */
+SELECT SUM(salary) AS Total_Salary_Paid FROM salaries;
+
+/********** 9) Commenting your queries *******/
+SELECT * FROM employees
+WHERE first_name='Mayumi' AND last_name='Schueller';
+
+/*********** 11) Filtering Data ***********/
+/* Get the list of all female employees */
+SELECT * FROM employees
+WHERE gender = 'F'
+LIMIT 10;
+
+/********** 12) AND OR *************/
+SELECT *
+FROM employees
+WHERE (first_name = 'Georgi' AND last_name='Facello' AND hire_date='1986-06-26')
+OR (first_name='Bezalel' AND last_name='Simmel');
+
+/* 13) How many female customers do we have from state of Oregon or New York? */
+SELECT COUNT(*) AS "NumberOfFemaleCustomers" 
+FROM customers
+WHERE gender='F' AND (state LIKE 'OR' OR state LIKE 'NY');
+
+/******** 15) NOT ***********/
+/* How many customers aren't 55? */
+SELECT COUNT(age) FROM customers
+WHERE NOT age=55;
+
+
+/***** 16) Comparison Operators *******/
+/* 17) Exercises */
+/* How many female customers do we have from the state of Oregon (OR)? */
+SELECT COUNT(*)
+FROM customers
+WHERE gender='F' AND state='OR';
+
+/* Who over the age of 44 has an income of 100 000 or more? */
+SELECT * 
+FROM customers
+WHERE age > 44 AND income=100000;
+
+/* Who between the ages of 30 and 50 has an income of less than 50 000? */
+SELECT *
+FROM customers
+WHERE age BETWEEN 30 AND 50
+AND income < 50000;
+
+/* What is the average income between the ages of 20 and 50? */
+SELECT AVG(income)
+FROM customers
+WHERE age BETWEEN 20 AND 50;
+
+
+/***** 18) Logical Operators AND OR NOT *****/
+/* 
+Order of Operations 
+FROM => WEHRE => SELECT 
+*/
+
+/***** 19) Operator Precedence ******/
+/* 
+(most importance to least importance)
+
+Parentheses
+Multiplication / Division
+Subtraction / Addition
+NOT
+AND
+OR
+
+If operators have equal precedence, then the operators are evaluated directionally.
+From Left to Right or Right to Left.
+
+check Operators Precedence.png
+*/
+
+SELECT state, gender FORM customers
+WHERE gender ='F' AND (state='NY' OR state='OR');
+
+/****** 20) Operator Precedence 2 ********/
+SELECT *
+FROM customers
+WHERE (
+	income > 10000 AND state='NY'
+	OR (
+		(age > 20 AND age < 30)
+		AND income <=20000
+	)
+) AND gender='F'
+
+/*Select people either under 30 or over 50 with an income above 50000 that are from either Japan or Australia*/
+SELECT *
+FROM customers
+WHERE (age < 30 OR age > 50)
+AND income > 50000
+AND (country = 'Japan' OR country = 'Australia');
+
+/*What was our total sales in June of 2004 for orders over 100 dollars?*/
+SELECT SUM(totalamount)
+FROM orders
+WHERE totalamount > 100
+AND orderdate='2004/06';
+
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