SELECT

Syntax

SELECT [ DISTINCT ]
{ * | projectItem [, projectItem ]* }
FROM tableExpression;

Test data

Example 1

• Test statements

  SELECT * FROM Table name;

• Test results

  a (VARCHAR)	b (INT)	c (DATE)
  a1	211	1990-02-20
  b1	120	2018-05-12
  c1	89	2010-06-14
  a1	46	2016-04-05

Example 2

• Test statements

  SELECT a, c AS d FROM Table name;

• Test results

  a (VARCHAR)	d (DATE)
  a1	1990-02-20
  b1	2018-05-12
  c1	2010-06-14
  a1	2016-04-05

Example 3

• Test statements

  SELECT DISTINCT a FROM Table name;

• Test results

  a (VARCHAR)
  a1
  b1
  c1

Subquery

Generally, a SELECT statement reads data from several tables, such as SELECT column_1, column_2 … FROM table_name. A SELECT statement can also read data from another SELECT statement, which is called a subquery.

• Sample statements

  INSERT INTO result_table
  SELECT * FROM
                 (SELECT   t.a,
                           sum(t.b) AS sum_b
                  FROM     t1 t
                  GROUP BY t.a
                 ) t1 
  WHERE  t1.sum_b > 100;

• Sample results

  a (VARCHAR)	b (INT)
  a1	211
  b1	120
  a1	257