Operators and Statements Flashcards
_
Underscore
Wildcard in LIKE statements, good for matching all characters but one.
SELECT * FROM FRIENDS WHERE last_name LIKE ‘_T’;
%
Modulo - In math calculations it gives remainder of a division problem.
Serves as wildcard in LIKE statements: SELECT * FROM —- WHERE —- LIKE ‘%_%’;
|| / CONCAT
Double Pipe: Concatenates two strings.
SELECT LASTNAME || ‘,’ || FIRSTNAME NAME FROM EMPLOYEES;
If employees accrue 12 days/yr, find all employees whose names start with B and who have more than 50 days of leave.
Lastname Years Leavetaken
SELECT LASTNAME, YEARS * 12 - LEAVETAKEN REMAINING
FROM VACATION
WHERE LASTNAME LIKE ‘B%’
AND YEARS * 12 - LEAVETAKEN > 50;
Logical Operators
AND, OR, NOT
UNION / UNION ALL
UNION: returns results of two queries and removes duplicate rows.UNION ALL: doesn’t remove duplicates.
SELECT * FROM –
UNION
SELECT * FROM –;
INTERSECT
Returns rows found in both queries.
SELECT * FROM –
INTERSECT
SELECT * FROM –;
MINUS
Returns rows from first query that were not present in second:
SELECT * FROM –
MINUS
SELECT * FROM –;
IN
Two ways:
SELECT * FROM – WHERE STATE = ‘TX’ OR STATE = ‘CA’;
SELECT * FROM – WHERE STATE IN (‘TX’, ‘CA’);
BETWEEN
Provides range. Two ways:
SELECT * FROM – WHERE PRICE > 10 AND PRICE < 20;
SELECT * FROM – WHERE PRICE BETWEEN 10 AND 20;
(Inclusive)
COUNT
Returns number of rows that satisfy condition in WHERE clause.
SELECT COUNT(*) alias FROM – WHERE –;
SUM
Returns sum of all values in a column. Only works on numbers.
SELECT SUM(COST) TOTAL FROM GROCERYLIST;
AVG
Average to take average of two columns:
SELECT AVG(HITS) / AVG(AB) TEAM_AVERAGE FROM TEAMSTATS;
MAX / MIN
MAX: Will return highest number in a column or word closest to Z.
MIN: opposite
ABS
Returns absolute value of a number.