PROC SQL
Phil Vecchione
SQL
• Structured Query Language
• Developed by IBM in the early 1970’s
• From the 70’s to the late 80’s there
were different types of SQL, based
on different databases.
• In 1986 the first unified SQL standard
(SQL-86) was created.
• Today the SQL parser that is used by
most databases are bases on SQL92 standards.
Proc SQL
• Added to the Base SAS package in
version 6
• Implemented to allow people familiar
with database to use SQL features
within SAS
• A “language within a language”
Anatomy of A PROC SQL
Statement
proc SQL;
select study, patient, age, race, gender
from work.demographics
where gender=‘M’
group by race;
quit;
But The SAS Data Step
Already Does That….
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•
SAS
SQL
Create dataset
• Create tables
• Update values
Update values
• Delete Records
Delete Records
Append new records • Insert New Records
• Create New
Create New
Variables
variables
• Sort Data
Sort data
• Join tables
Merge datasets
So what’s so cool about proc SQL?
The Power Of SQL
• SQL looks at datasets differently from SAS
– SAS looks at a dataset one record at a time, using
an implied loop that moves from the first record to
the last
– SQL looks at all the records, as a single object
• Because of this difference SQL can easily do
a few things that are more difficult to do in
SAS
Power of SQL: SQL Functions
• There are a number of built in functions in
SQL that can be used in a select statement
• Because of how SQL handles a dataset,
these functions work over the entire dataset
• Functions:
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–
–
–
–
Count: Counts Values
Sum: Sums Values
Max: Identifies the largest value
Min: Identifies the smallest value
Mean: Averages the values
SQL Functions: Example
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proc sql;
select count(*) as Records
from orcl.pat_survey1
quit;
RECORDS
-------19
Power of SQL: Group By
• Similar to the BY parameter
used in SAS
• Groups the SQL observations by
the variable defined
• When used with the SQL
functions allows summary
information on groupings rather
then the entire dataset
Group By: Example
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proc sql;
select site_n, count(*) as Records
from orcl.pat_survey1
group by site_n;
quit;
SITE_N
RECORDS
---------------107
1
998
1
2310
2
2344
1
Loading Macro Variables
• A great feature of Proc SQL is
that you can load a value or
values from a SQL statement
into a macro variable
• Can put a specific value into a
macro variable for use
throughout your program
• Coupled with the SQL functions,
you can load calculated values
into a macro variable
Loading Macro Variables:
Example
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proc sql;
select mean(rhin_age)
into: meanage
from orcl.pat_survey1
where rhin_age is not null;
quit;
%put The mean age is: &meanage;
AVG
-----------33.35294
The mean age is: 33.35294
Power of SQL: Merging
Between Two Values
• A merge using a SAS data step requires
that the variable described in the BY
parameter have an EXACT match
• SQL joins can contain NON-EXACT
parameters for a join
• Thus, allowing for joins to occur
between values
Merging Between Two Values:
Example
Drug Dosing
Drug Concentrations
Patient Visit Date
Conc
1
4/14/2003
12
2
4/10/2003
3
3
4/4/2003
99
Patient Start Drug
End Drug
1
4/13/2003
4/15/2003
1
4/19/2003
4/21/2003
2
3/22/2003
3/25/2003
2
4/9/2003
4/11/2003
3
3/1/2003
3/3/2003
3
5/9/2003
5/11/2003
Merging Between Two Values:
Example
Drug Dosing
Drug Concentrations
Patient Visit Date
Conc
1
4/14/2003
12
2
4/10/2003
3
3
4/4/2003
99
proc sql;
select c.patient,
c.visit_date,
c.conc,d.start_date,
d.end_date
from drug_conc c,
drug_dosing d
where c.patient=d.patient;
quit;
Patient Start Date
End Date
1
4/13/2003
4/15/2003
1
4/19/2003
4/21/2003
2
3/22/2003
3/25/2003
2
4/9/2003
4/11/2003
3
3/1/2003
3/3/2003
3
5/9/2003
5/11/2003
Merging Between Two Values:
Example
Drug Concentrations
Patient Visit Date
Conc
1
4/14/2003
12
2
4/10/2003
3
3
4/4/2003
99
select c.patient,
c.visit_date,
c.conc,d.start_date,
d.end_date
from drug_conc c,
drug_dosing d
where c.patient=d.patient
and (d.start_date le
c.visit_date le
d.end_date);
Drug Dosing
Patient Start Date
End Date
1
4/13/2003
4/15/2003
1
4/19/2003
4/21/2003
2
3/22/2003
3/25/2003
2
4/9/2003
4/11/2003
3
3/1/2003
3/3/2003
3
5/9/2003
5/11/2003
References
• Books
– SAS Guide to the SQL Procedure
– SQL for Dummies
• Papers
– SQL for People Who Don’t Think They
Need SQL: Erin Christen (PharmaSUG
2003)
Thank You
Any Questions?