To ANSI or Not To ANSI

Gravenstein, Costello, Maurer

Amtrust Bank

Session #420

Speaker Qualifications

Rumpi Gravenstein, Application Developer, Senior, Amtrust Bank

Newsletter Editor, North East Ohio Oracle Users Group

Has been working with Oracle since 1988 Past Presenter at meetings of:

Independent Oracle Users Group North East Ohio Oracle Users Group

Agenda

Brief History Review Join Technologies Analysis Recommendation

ANSI/Oracle Support History

ANSI here refers to SQL/99 Join Syntax The standard to which all RDBMS vendors

strive to comply

SQL/99 support started with Oracle 9i in 2001 Two years after the release of the standard,

Oracle supports it.

This presentation restricted to the Oracle implementation of the ANSI standard

3 Join Condition Types

Equijoin Columns with the same name Columns with different names

Outerjoin Left (left driving table) Right (right driving table) Full (both tables driving)

Cross/Cartesian product

Traditional Equijoin - Same Name

Traditional Oracle Approach

SELECT e.ename AS Employee_name,

d.deptno,

d.dname AS Department_name

FROM emp e,

dept d

WHERE e.deptno = d.deptno;

Table prefix is required to remove ambiguity on

common columns

Join conditions must be listed

ANSI Equijoin Natural Syntax

ANSI SQL Natural Join

SELECT ename AS employee_name,

deptno,

dname AS department_name

FROM emp

NATURAL JOIN dept;

Join columns implied, based on columns that have the same name

No table prefix if column is part of join condition.

No commas between tables.

God forbid that you accidentally add a non-join column to both tables…(um.. audit columns...)

ANSI Equijoin Using Syntax

ANSI SQL Join USING

SELECT d.dname,

e.ename

FROM emp d

JOIN dept d USING ( deptno );

Several columns share same name, only joining on some of them, in this

case deptno

Table prefix allowed on columns that are not part of the using clause

(join condition)

Add additional join columns using( deptno, join_col2, join_col3, …)

Traditional Equijoin Syntax

Traditional Join, columns different

SELECT d.department_name,

l.city

FROM departments d,

locations l

WHERE d.location_id = l.id;

Join column names are different

ANSI On Equijoin Syntax

ANSI SQL ON

SELECT d.department_name,

l.city

FROM departments d

JOIN locations l ON ( d.location_id = l.id );

Use ON when join column names are different

List join conditions here like traditional syntax

ANSI Equijoin Syntax

ANSI SQL Multi Table On

SELECT e.empno,

l.loc_id,

d.dname,

l.state_tx

FROM locations l

JOIN dept d ON ( d.location_id = l.id )

JOIN emp e ON ( d.deptno = e.deptno );

Bring in first table join

Bring in second table join Any prior table column is visible – joins from left to right

No commas between tables

ANSI Equijoin Syntax

ANSI SQL INNERSELECT e.emp_id,

l.city,

d.dept_name,

d.deptno

FROM locations l

INNER JOIN dept d ON ( d.location_id = l.id )

INNER JOIN emp e ON d.deptno = e.deptno;

INNER – an optional keyword stating this is an equijoin (not an

outer or cross join)

ON clause requires reference to join columns by table name to

resolve ambiguity

Parenthesis are optional, we like to include them for clarity

Traditional Outerjoin Syntax

Traditional Outer Join

SELECT e.ename,

d.dname

FROM emp e,

dept d

WHERE e.deptno (+) = d.deptno

Traditional Outer Join Notation(+) indicator denotes expand records on this side if needed

NULL in name if no employees in the department.

ANSI Outerjoin Syntax

Left Outer Join

SELECT e.ename,

d.dname

FROM dept d

LEFT OUTER JOIN emp e

ON (e.deptno = d.deptno);

LEFT denotes that the dominant table is to the left (dept) and that all of it’s rows will be returned. The

right table is expanded with NULL records

NULL in last name if no employees in the department.

OUTER keyword is optional.

ANSI Outerjoin Syntax

Left Outer Join

SELECT e.ename,

d.dname

FROM dept d

NATURAL LEFT JOIN emp e;

NATURAL can be used in an INNER and OUTER join.

We don’t recommend using it here either!

USING e.g. LEFT JOIN emp e USING (deptno)can be used in an INNER and OUTER join.

ANSI Outerjoin Syntax

Right Outer Join

SELECT e.ename,

d.dname

FROM emp e

RIGHT OUTER JOIN dept d

ON (e.deptno = d.deptno);

RIGHT OUTER denotes that the dominant table is to the right. The left table gets expanded with

NULLS.

NULL in last name if no employees in the department.

Traditional Outerjoin Syntax -Close

Full Outer Join Can only be represented with a “UNION” query.

SELECT e.ename,

d.dname

FROM emp e, dept d

WHERE e.deptno (+) = d.deptno

UNION

SELECT e.ename,

d.dname

FROM emp e, dept d

WHERE e.deptno = d.deptno (+)

Shouldn’t see many of these(We’ve never needed one)

UNION ALL is incorrect as it results in duplicate rows

UNION performs an implicit “DISTINCT” on result – possibly

removing desired rowsThis “full” join syntax can be found

on internet as “true” full join

Traditional Full Close-Executionscott@VOTER> SELECT e.ename, 2 d.dname 3 FROM emp e, dept d 4 WHERE e.deptno (+) = d.deptno 5 UNION 6 SELECT e.ename, 7 d.dname 8 FROM emp e, dept d 9 WHERE e.deptno = d.deptno (+) 10 ;

16 rows selected.

Execution Plan---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=15 Card=28 Bytes=588) 1 0 SORT (UNIQUE) (Cost=15 Card=28 Bytes=588) 2 1 UNION-ALL 3 2 HASH JOIN (OUTER) (Cost=7 Card=14 Bytes=294) 4 3 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60) 5 3 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=126) 6 2 HASH JOIN (OUTER) (Cost=7 Card=14 Bytes=294) 7 6 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=126) 8 6 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60)

Plan reflects the implicit DISTINCT inherent in UNION

clause

Notice Cost 15

Traditional Full Join - True

SELECT e.ename, d.dname FROM emp e, dept d WHERE e.deptno = d.deptno(+)UNION ALLSELECT NULL, d.dname FROM dept d WHERE NOT EXISTS (SELECT 1 FROM emp e WHERE e.deptno = d.deptno)

Outer join emp table with the dept table – all emp rows now

returned

Add Dept rows that have no match from emp

Use UNION ALL to avoid implicit DISTINCT inherent in UNION

This syntax can be found on internet at http://optimizermagic.blogspot.com under post on “Outerjoins in Oracle”

Traditional Full Join True-Execution

scott@VOTER> SELECT e.ename, d.dname 2 FROM emp e, dept d 3 WHERE e.deptno = d.deptno(+) 4 UNION ALL 5 SELECT NULL, d.dname 6 FROM dept d 7 WHERE NOT EXISTS 8 (SELECT 1 9 FROM emp e 10 WHERE e.deptno = d.deptno);

16 rows selected.

Execution Plan---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=13 Card=16 Bytes=324) 1 0 UNION-ALL 2 1 HASH JOIN (OUTER) (Cost=7 Card=14 Bytes=294) 3 2 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=126) 4 2 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60) 5 1 HASH JOIN (ANTI) (Cost=7 Card=2 Bytes=30) 6 5 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60) 7 5 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=42)

Explain plan for “True” traditional outer join – SORT (UNIQUE)

missing

Cost 13 here, prior plan had cost of 15

ANSI Outerjoin Syntax

Full Outer Join

SELECT e.ename,

d.dname

FROM emp e

FULL OUTER JOIN dept d

ON (e.deptno = d.deptno);

FULL OUTER denotes that the table to the right AND the table to the left will have all their

records returned

NULL in last name if no employees in the department.

NULL in department name if employee not in a department.

OUTER is optional

ANSI Full Execution Planscott@VOTER> SELECT e.ename, 2 d.dname 3 FROM emp e 4 FULL OUTER JOIN dept d 5 ON (e.deptno = d.deptno);

16 rows selected.

Execution Plan---------------------------------------------------------- 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=13 Card=16 Bytes=256) 1 0 VIEW (Cost=13 Card=16 Bytes=256) 2 1 UNION-ALL 3 2 HASH JOIN (OUTER) (Cost=7 Card=14 Bytes=294) 4 3 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=126) 5 3 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60) 6 2 HASH JOIN (ANTI) (Cost=7 Card=2 Bytes=30) 7 6 TABLE ACCESS (FULL) OF 'DEPT' (TABLE) (Cost=3 Card=5 Bytes=60) 8 6 TABLE ACCESS (FULL) OF 'EMP' (TABLE) (Cost=3 Card=14 Bytes=42)

Cost 13 = Cost of Traditional True

Traditional Cross Join/Cross Product

Cross Join

SELECT emp_id,

ename,

dname

FROM emp e,

dept d

WHERE d.deptno = 10;

No join condition between tables… um, normally not good.

Inadvertent cross join not obvious if joined table has a single row

ANSI Cross Join/Cross Product

Cross Join

SELECT emp_id,

ename,

dname

FROM emp e

CROSS JOIN dept d

WHERE d.deptno = 10;

Explicit CROSS condition, impossible to do this accidentally.

ANSI Correlated Join

Correlated Query Syntax Join

SELECT empno,

ename

FROM emp e

WHERE EXISTS

( SELECT NULL

FROM dept d

INNER JOIN locations l

ON ( l.loc_id = d.loc )

WHERE d.deptno = e.deptno

);

ANSI doesn’t allow join clause on first table

Only tables in “current” FROM clause visible to

ANSI join logic

Not really a “mixed” syntax join

ANSI Correlated Subquery Issues

SELECT * FROM dept d INNER JOIN locations2 l USING ( loc ) WHERE EXISTS ( SELECT NULL FROM emp e WHERE e.loc = l.loc )

ORA-25154: column part of USING clause cannot have qualifier

Don’t be tempted to remove the table prefix “l”

“NATURAL” joins have the same issue

Scope of reference dictates that the closest column be used

ANSI Outer Join Subtleties

SELECT d.deptno, e.ename, e.job  FROM dept d        LEFT JOIN emp e         ON (    e.deptno = d.deptno             AND e.job = 'SALESMAN');

DEPTNO ENAME JOB====== ====== ========

30    ALLEN    SALESMAN30    WARD    SALESMAN 30    MARTIN   SALESMAN30    TURNER   SALESMAN50        40        20        10   

Filter is applied before join is executed

A number of rows returned that have “OUTER” joined emp data

Only dept 30, Sales, has SALESMAN as a job.

ANSI Outer Join Subtleties

SELECT d.deptno, e.ename, e.job  FROM dept d        LEFT JOIN emp e         ON (    e.deptno = d.deptno) WHERE e.job = 'SALESMAN';

DEPTNO ENAME JOB====== ====== ========

30    ALLEN    SALESMAN30    WARD     SALESMAN30    MARTIN   SALESMAN30    TURNER   SALESMAN   

Filter is applied after join is executed

No outer joined data

The condition has effectively converted this OUTER JOIN query to an INNER JOIN

Mixed Traditional/ANSI Join

Mixed Syntax Join

SELECT emp_id,

ename,

dname

FROM emp e

INNER JOIN dept d USING (deptno),

dual

WHERE deptno = 10;

Uhg….Choose one or the other,

but not both please!

Oracle will run this without throwing an error

Presentation Bonus – This section not in conference

proceedings.

Mixed Syntax Join

scott@VOTER> SELECT empno, 2 ename, 3 dname, 4 dummy 5 FROM dual, 6 emp e 7 INNER JOIN dept d ON (d.deptno = e.deptno) 8 WHERE e.deptno = 10;

EMPNO ENAME DNAME D---------- ---------- -------------- - 7782 CLARK ACCOUNTING X 7839 KING ACCOUNTING X 7934 MILLER ACCOUNTING X

3 rows selected.

Oracle will run this without throwing an error

Multiple traditional and ANSI sections are allowed

Mixed Syntax Join

scott@VOTER> SELECT empno, 2 ename, 3 dname, 4 dummy 5 FROM emp e 6 dual, 7 INNER JOIN dept d 8 ON ( d.deptno = e.deptno ) 9 WHERE e.deptno = 10; dual, *ERROR at line 6:ORA-00933: SQL command not properly ended

Traditional mixed in between ANSI

Mixed Syntax Join

SELECT empno, ename, dname, dummy

FROM dual, emp e INNER JOIN dept d on d.deptno = e.deptno and dummy IS NOT NULL WHERE e.deptno = 10;

and dummy IS NOT NULL

*

ERROR at line 8:

ORA-00904: "DUMMY": invalid identifier

ANSI joins can only see other tables taking part in ANSI join

Presence of both comma (Traditional) and JOIN Mixed syntax join

ANSI vs Traditional Join Analysis

Impact areas Code Clarity

Readability Join Errors

Flexibility Ease of Use

Developer Training DBA Training

Legacy Code Standards

Code Clarity – Readability (Traditional) SELECT /*+ qb_name(orig) */ fdla.dim_borrower_v_id dim_borrower_v_id FROM dim_as_of_date_vw daod, dim_daily_loan_applctn_detl ddlad, dim_disbursement_date_vw dddv, dim_loan_originator dlo, fact_daily_loan_application fdla, dim_loan_applctn_status_vw dlasv WHERE daod.dim_as_of_date_v_id = ddlad.dim_as_of_date_v_id AND daod.dim_as_of_date_v_id = fdla.dim_as_of_date_v_id AND ddlad.dim_daily_loan_applctn_detl_id =fdla.dim_daily_loan_applctn_detl_id AND ddlad.dim_as_of_date_v_id = fdla.dim_as_of_date_v_id AND dddv.dim_disbursement_date_v_id = fdla.dim_disbursement_date_v_id AND dlo.dim_loan_originator_id = fdla.dim_loan_originator_id AND dlasv.DIM_LOAN_APPLCTN_STATUS_V_ID = fdla.DIM_LOAN_APPLCTN_STATUS_V_ID AND NOT (dlasv.STATUS_CODE BETWEEN '700' AND '740') AND NOT (dlasv.status_code BETWEEN '000' AND '429') AND daod.as_of_calendar_date = (CASE WHEN &in_DATE_SLICE IS NULL THEN LAST_DAY (ADD_MONTHS (TRUNC(SYSDATE), -1)) + &c_DEFAULT_SLICE_OFFESET ELSE TO_DATE( &in_DATE_SLICE, &c_DATE_FORMAT ) END) AND dddv.disburse_date BETWEEN

TRUNC(NVL(TO_DATE(&in_START_REPORT_MONTH,&c_DATE_FORMAT),ADD_MONTHS(SYSDATE, -1)), 'MM') AND TRUNC (LAST_DAY

(NVL(TO_DATE(&in_END_REPORT_MONTH,&c_DATE_FORMAT),ADD_MONTHS(SYSDATE, -1)))) AND ddlad.loan_transfer_status_code != 'T'

Can you quickly determine how tables

are joined?

This is a real join we’ve implemented as part of

a recent project

Code Clarity – Readability (ANSI)SELECT /*+ qb_name(orig) */ fdla.dim_borrower_v_id dim_borrower_v_id FROM dim_as_of_date_vw daod INNER JOIN fact_daily_loan_application fdla ON (daod.dim_as_of_date_v_id = fdla.dim_as_of_date_v_id) INNER JOIN dim_daily_loan_applctn_detl ddlad ON ( ddlad.dim_as_of_date_v_id = daod.dim_as_of_date_v_id AND ddlad.dim_daily_loan_applctn_detl_id = fdla.dim_daily_loan_applctn_detl_id AND ddlad.dim_as_of_date_v_id = fdla.dim_as_of_date_v_id ) INNER JOIN dim_disbursement_date_vw dddv ON ( dddv.dim_disbursement_date_v_id = fdla.dim_disbursement_date_v_id) INNER JOIN dim_loan_originator dlo ON (dlo.dim_loan_originator_id = fdla.dim_loan_originator_id) INNER JOIN dim_loan_applctn_status_vw dlasv ON (dlasv.dim_loan_applctn_status_v_id = fdla.dim_loan_applctn_status_v_id) WHERE NOT (dlasv.STATUS_CODE BETWEEN '700' AND '740') AND NOT (dlasv.status_code BETWEEN '000' AND '429') AND daod.as_of_calendar_date = (CASE WHEN &in_DATE_SLICE IS NULL THEN LAST_DAY (ADD_MONTHS (TRUNC(SYSDATE), -1)) + &c_DEFAULT_SLICE_OFFESET ELSE TO_DATE( &in_DATE_SLICE, &c_DATE_FORMAT ) END) AND dddv.disburse_date BETWEEN

TRUNC(NVL(TO_DATE(&in_START_REPORT_MONTH,&c_DATE_FORMAT),ADD_MONTHS(SYSDATE, -1)), 'MM') AND TRUNC (LAST_DAY

(NVL(TO_DATE(&in_END_REPORT_MONTH,&c_DATE_FORMAT),ADD_MONTHS(SYSDATE, -1)))) AND ddlad.loan_transfer_status_code != 'T'

TableJoinConditionsAreEasilyIdentified

Code Clarity – Join Errors

Traditional SyntaxSELECT col1,

col2,

...

FROM tab1 t1,

tab2 t2,

...

WHERE ...

Is a table join condition missing? How do you know?

Code Clarity – Join Errors

ANSI SyntaxSELECT col1,

col2,

...

FROM tab1 t1

[join type] tab2 t2

[join condition]

...

WHERE ...

must identify join type:INNEROUTERFULL

CROSS

Identifies join condition USING or ON

“Impossible” to do inadvertent CROSS join

Flexibility – (+) Restrictions not present in ANSI

You cannot specify the (+) operator in a query block that also contains FROM clause join syntax. The (+) operator can appear only in the WHERE clause or, in the context of left-correlation (that is, when specifying

the TABLE clause) in the FROM clause, and can be applied only to a column of a table or view. If A and B are joined by multiple join conditions, then you must use the (+) operator in all of these conditions. If you

do not, then Oracle Database will return only the rows resulting from a simple join, but without a warning or error to advise you that you do not have the results of an outer join.

The (+) operator does not produce an outer join if you specify one table in the outer query and the other table in an inner query.

You cannot use the (+) operator to outer-join a table to itself, although self joins are valid. For example, the following statement is not valid:

SELECT employee_id, manager_id FROM employees WHERE employees.manager_id(+) = employees.employee_id;

However, the following self join is valid:

SELECT e1.employee_id, e1.manager_id, e2.employee_id FROM employees e1, employees e2 WHERE e1.manager_id(+) = e2.employee_id;

The (+) operator can be applied only to a column, not to an arbitrary expression. However, an arbitrary expression can contain one or more columns marked with the (+) operator.

A WHERE condition containing the (+) operator cannot be combined with another condition using the OR logical operator.

A WHERE condition cannot use the IN comparison condition to compare a column marked with the (+) operator with an expression.

A WHERE condition cannot compare any column marked with the (+) operator with a subquery.

“Oracle strongly recommends that you use the more flexible FROM

clause (ANSI) join syntax”

Ease of Use/Developer & DBA Training Traditional Join

Long time Oracle developers do nothing New Oracle Developers need to learn Oracle

syntax ANSI Join

Works with SQL Server/Oracle/MySQL/… Syntax is more readable/self documenting Natural join is “un-natural” - can lead to errors

Installed Code Base

ANSI Joins not present in the Oracle installed code base

ANSI Joins present in other RDBMS installed code More of these databases coming all the time

Harm in having two join syntaxes Support personnel have to be comfortable with

both syntaxes Additional training required

Fishbone Diagram

Cod

e C

larit

yFe

wer

Joi

n

Con

ditio

n E

rror

s

Error FreeSQL

Only Support

One Coding

Style

Mul

ti-V

endo

r

RD

BM

S

Sup

port

Only Allow Traditional Join Syntax

Allow ANSI Join Syntax

Sta

ndar

ds B

ased

Feat

ure

Ric

h

Installed Oracle

Code Base

No Natural Join

Possibility

Recommendations

Allow both Provide training so that all are familiar with both Place some restrictions on ANSI syntax to prevent

problems Do not allow NATURAL joins and possibly USING

clause Single SQL statements should use one or the other

but not both New development should try to use same syntax

throughout Long term goal, ANSI only

Session Goals

Familiarity with ANSI Join Syntax Understanding the merits of the ANSI join

syntax Intention to start using the ANSI syntax

?

Questions

Thank You

Please complete the evaluation forms My Name: Rumpi Gravenstein Session Title: To ANSI or not to ANSI Session #: 420 If you have additional questions, I can be

reached at rgravenstein@amtrust.com