Basic SQL Queries

Below are the basic SQL Queries which you might need to use frequently.
Note: The Quotes “‘” may have a different Unicode value and you may need to replace them with the good ones.

Select Unique entries :

SELECT DISTINCT column_name_1, column_name_2, …
FROM table_name;

Select the Count :

SELECT COUNT(column_name) FROM table_name;

Using IS NULL & IS NOT NULL :

SELECT column_name FROM table_name WHERE column_name IS NULL;

Using CASE :

SELECT column_name,
CASE
WHEN condition_1 THEN ‘Result_A’
WHEN condition_2 THEN ‘Result_B’
ELSE ‘Result_C’
END
FROM table_name;

Using MIN & MAX :

SELECT MIN(column_name) FROM table_name WHERE condition;
SELECT MAX(column_name) FROM table_name WHERE condition;

Using IN Keyword :

SELECT column_name FROM table_name WHERE column_name IN (value1, value2, …);

INNER JOIN :

SELECT column_name(s)
FROM table_name_1
JOIN table_name_2
ON table_name_1.column_name_1 = table_name_2.column_name_2;

LEFT JOIN :

SELECT column_name(s)
FROM table_name_1
LEFT JOIN table_name_2
ON table_name_1.column_name_1 = table_name_2.column_name_2;

RIGHT JOIN :

SELECT column_name(s)
FROM table_name_1
RIGHT JOIN table_name_2
ON table_name_1.column_name_1 = table_name_2.column_name_2;

OUTER JOIN :

SELECT column_name(s)
FROM table_name_1
FULL OUTER JOIN table_name_2
ON table_name_1.column_name_1 = table_name_2.column_name_2
WHERE condition;

SELF JOIN :

SELECT column_name(s)
FROM table_name_1 T1, table_name_1 T2
WHERE T1.column_name_1 <condition> T2.column_name_2;

Using ORDER BY :

SELECT column_name FROM table_name ORDER BY column_name ASC –OR DESC;

Using UNION :

SELECT column_name(s) FROM table_name_1
UNION
SELECT column_name(s) FROM table_name_2;

Select INTO :

SELECT * INTO table_new FROM table_old WHERE condition;

Using INSERT :

INSERT INTO table_name (column_name_1, column_name_2, column_name_3)
VALUES (value_1, value_2 , value_3);

Using INSERT INTO SELECT :

INSERT INTO table_name_2 SELECT * FROM table_name_1 WHERE condition;

CREATE TABLE :

CREATE TABLE table_name (
column_1 datatype_1,
column_2 datatype_2,
column_3 datatype_3
);

TRUNCATE TABLE (This will remove all the rows but will keep the structure as is) :

TRUNCATE TABLE table_name;

DROP TABLE (This will remove all the rows as well as the definition) :

DROP TABLE table_name;

ALTER Table :

ALTER TABLE table_name ADD column_name datatype;

CREATE INDEX :

CREATE INDEX index_name ON table_name (column_name_1, column_name_2, …);

CREATE VIEW :

CREATE VIEW view_name AS SELECT column_name_1, column_name_2, …
FROM table_name WHERE condition;

Also view : PL/SQL Reference