Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. : Subquery « Subquery « SQL Server / T-SQL Tutorial

5> CREATE TABLE titles(
6>    title_id       varchar(20),
7>    title          varchar(80)       NOT NULL,
8>    type           char(12)          NOT NULL,
9>    pub_id         char(4)               NULL,
10>    price          money                 NULL,
11>    advance        money                 NULL,
12>    royalty        int                   NULL,
13>    ytd_sales      int                   NULL,
14>    notes          varchar(200)          NULL,
15>    pubdate        datetime          NOT NULL
16> )
17> GO
1>
2> insert titles values ('1', 'Secrets',   'popular_comp', '1389', $20.00, $8000.00, 10, 4095,'Note 1','06/12/94')
3> insert titles values ('2', 'The',       'business',     '1389', $19.99, $5000.00, 10, 4095,'Note 2','06/12/91')
4> insert titles values ('3', 'Emotional', 'psychology',   '0736', $7.99,  $4000.00, 10, 3336,'Note 3','06/12/91')
5> insert titles values ('4', 'Prolonged', 'psychology',   '0736', $19.99, $2000.00, 10, 4072,'Note 4','06/12/91')
6> insert titles values ('5', 'With',      'business',     '1389', $11.95, $5000.00, 10, 3876,'Note 5','06/09/91')
7> insert titles values ('6', 'Valley',    'mod_cook',     '0877', $19.99, $0.00,    12, 2032,'Note 6','06/09/91')
8> insert titles values ('7', 'Any?',      'trad_cook',    '0877', $14.99, $8000.00, 10, 4095,'Note 7','06/12/91')
9> insert titles values ('8', 'Fifty',     'trad_cook',    '0877', $11.95, $4000.00, 14, 1509,'Note 8','06/12/91')
10> GO

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)
1>
2>
3> CREATE TABLE roysched(
4>    title_id       varchar(20),
5>    lorange        int                   NULL,
6>    hirange        int                   NULL,
7>    royalty        int                   NULL
8> )
9> GO
1>
2>
3> insert roysched values('1', 0, 10000, 10)
4> insert roysched values('2', 10001, 20000, 12)
5> insert roysched values('3', 20001, 30000, 14)
6> insert roysched values('4', 30001, 40000, 16)
7> insert roysched values('5', 40001, 50000, 18)
8>
9> GO

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)

(1 rows affected)
1>
2>
3>
4> SELECT titles.title_id, title, royalty
5> FROM titles
6> WHERE titles.royalty >=
7>     (SELECT 1.25 * roysched.royalty FROM roysched)
8>
9> GO
Msg 512, Level 16, State 1, Server J\SQLEXPRESS, Line 4
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
1>
2> drop table titles;
3> drop table roysched;
4> GO
1>
2>

8.1.Subquery
	8.1.1.	Building a Nested Subquery
	8.1.2.	Using Subqueries to Check for the Existence of Matches
	8.1.3.	Using Subqueries to Check for the Existence of Matches between two tables
	8.1.4.	Subqueries are SELECT statements that are nested within another T-SQL statement.
	8.1.5.	Subqueries and Comparison Operators: =
	8.1.6.	A subquery can be used with other comparison operators: <
	8.1.7.	Subqueries and IN Operator
	8.1.8.	A query that uses three subqueries
	8.1.9.	Doing calculation with subquery
	8.1.10.	Subqueries can be nested.
	8.1.11.	ID NOT IN (SELECT ID FROM Title)
	8.1.12.	Delete with subquery
	8.1.13.	Join and sub query
	8.1.14.	Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
	8.1.15.	subquery with >=
	8.1.16.	<> ALL with subquery