command

select STRAIGHT_JOIN
	ps_class_instr.CRSE_ID,
	ps_class_instr.STRM,
	ENRL_TOT,
	EMPLID as 'INSTR',
	ACTUAL_ENRL_TOT as 'COURSE_ENRL_TOT',
	GRDE_ENRL_TOT as 'GRDE_ENRL_TOT',
	ps_class_instr.CLASS_SECTION as 'CLASS_SCTN',
	CLASS_NBR as 'CLASS_NBR',
	ACAD_GROUP as 'ACAD_GROUP',
	SUBJECT as 'SBJ',
	CATALOG_NBR as 'CATALOG_NBR',
	DESCR,
	ROUND(GRADE_AVG, 3) as GRADE_AVG,
	GRADE_AVG_RANK,
	(@total - GRADE_AVG_RANK)/@total as 'GRADE_AVG_PCT',
	ROUND(GPA, 3) as GPA,
	ROUND(DIFFICULTY01, 3) as DIFF1,
	round(UNIT_AVG, 2) as 'Q_UNIT_AVG'
from 
ps_class_instr USE INDEX FOR JOIN (FULL)
join
Course
on
ps_class_instr.CRSE_ID=Course.CRSE_ID and ps_class_instr.STRM=Course.STRM and ps_class_instr.CLASS_SECTION=Course.CLASS_SECTION
where SUBJECT='CS' and CATALOG_NBR LIKE '221%';

results

+----+-------------+----------------+------+---------------------------------------------+------+---------+---------------------------------------------------------------+---------+-------------
| id | select_type | table          | type | possible_keys                               | key  | key_len | ref                                                           | rows    | Extra       
+----+-------------+----------------+------+---------------------------------------------+------+---------+---------------------------------------------------------------+---------+-------------
|  1 | SIMPLE      | ps_class_instr | ALL  | FULL                                        | NULL | NULL    | NULL                                                          | 1497401 |             
|  1 | SIMPLE      | Course         | ref  | STRM,FULL,SUBJECT_AND_CATALOG,CLASS_SECTION | FULL | 778     | august.ps_class_instr.CRSE_ID,august.ps_class_instr.STRM,func |       1 | Using where 
+----+-------------+----------------+------+---------------------------------------------+------+---------+---------------------------------------------------------------+---------+------------

SHOW CREATE TABLE ps_class_instr\G;

*************************** 1. row ***************************
       Table: ps_class_instr
Create Table: CREATE TABLE `ps_class_instr` (
  `CRSE_ID` varchar(6) NOT NULL,
  `CRSE_OFFER_NBR` int(38) NOT NULL,
  `STRM` varchar(4) NOT NULL,
  `SESSION_CODE` varchar(3) NOT NULL,
  `CLASS_SECTION` varchar(4) NOT NULL,
  `CLASS_MTG_NBR` int(38) NOT NULL,
  `INSTR_ASSIGN_SEQ` int(38) NOT NULL,
  `EMPLID` varchar(255) DEFAULT NULL,
  `INSTR_ROLE` varchar(4) NOT NULL,
  `GRADE_RSTR_ACCESS` varchar(1) NOT NULL,
  `CONTACT_MINUTES` int(38) NOT NULL,
  `SCHED_PRINT_INSTR` varchar(1) NOT NULL,
  `INSTR_LOAD_FACTOR` float(10,4) NOT NULL,
  `EMPL_RCD` int(38) NOT NULL,
  `ASSIGN_TYPE` varchar(3) NOT NULL,
  `WEEK_WORKLOAD_HRS` float(5,2) NOT NULL,
  `ASSIGNMENT_PCT` float(5,2) NOT NULL,
  `AUTO_CALC_WRKLD` varchar(1) NOT NULL,
  KEY `STRM` (`STRM`),
  KEY `FULL` (`CRSE_ID`,`STRM`,`CLASS_SECTION`),
  KEY `INSTR_ROLE` (`INSTR_ROLE`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1