proc sql talk 12

8/10/2019 Proc SQL Talk 12

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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, basedon different databases.

• In 1986 the first unified SQL standard(SQL-86) was created.

• Today the SQL parser that is used bymost databases are bases on SQL-92 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

Statementproc SQL;

select study, patient, age, race, gender

from work.demographicswhere gender=„M‟

group by race;

quit;



But The SAS Data Step

Already Does That….

• Create dataset

• Update values

• Delete Records

• Append new records

• Create New

variables

• Sort data

• Merge datasets

• Create tables

• Update values

• Delete Records

• Insert New Records

• Create New

Variables• Sort Data

• Join tables

SAS SQL

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:

– Count: Counts Values

– Sum: Sums Values

– Max: Identifies the largest value

– Min: Identifies the smallest value

– Mean: Averages the values



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

21 proc sql;

22 select site_n, count(*) as Records

23 from orcl.pat_survey1

24 group by site_n;

25 quit;

SITE_N RECORDS

----------------

107 1

998 1

2310 2

2344 1



Loading Macro Variables

• A great feature of Proc SQL isthat you can load a value orvalues from a SQL statement

into a macro variable• Can put a specific value into a

macro variable for usethroughout your program

• Coupled with the SQL functions,you can load calculated valuesinto a macro variable



Loading Macro Variables:

Example43 proc sql;

44 select mean(rhin_age)

45 into: meanage

46 from orcl.pat_survey1

47 where rhin_age is not null;

48 quit;

50 %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 occurbetween values



Merging Between Two Values:

Example

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

Drug Concentrations Drug Dosing




Example


1 4/14/2003 12

2 4/10/2003 3

3 4/4/2003 99

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

Drug Dosing

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;

Drug Concentrations




Example


1 4/14/2003 12

2 4/10/2003 3

3 4/4/2003 99

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

Drug Concentrations Drug Dosing

select c.patient,

c.visit_date,

c.conc,d.start_date,

d.end_datefrom drug_conc c,

drug_dosing d

where c.patient=d.patient

and (d.start_date le

c.visit_date le

d.end_date);



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)

proc sql talk 12

Documents