This article expands on on the Database Design Pattern: The Lookup Table article from last month. You can check that article for the merits of using lookup tables. The key to using lookup tables that serve multiple purposes is defining part of the natural key as a non-unique super key. That super key allows you to return unique results sets from a single table. Each result set could be in its own table but that causes you to create a lot of small tables. The natural key in a WHERE clause lets you discover the surrogate key, which you should use as the primary key. This article shows how you can rewrite the examples from that article into HTML fragment. Then, you can use the HTML fragment in a web form. This article has two parts. They are: How to write an HTML fragment from a lookup table How to use an HTML fragment in a web form The first part shows you how to create a list of OPTION tags, and the second shows you how to use the OPTION tags in a web form. How to write an HTML fragment from a lookup table The lookup table in this article differs slightly from the one in the other article. The lookup table is renamed the common_lookup table, and several additional columns have been added. For example, the common_lookup table includes the four common columns that audit who created and last updated each row in the table. This is the description of the common_lookup table: SQL> desc common_lookup Name Null? Type ----------------------------------------- -------- ---------------------------- COMMON_LOOKUP_ID NOT NULL NUMBER COMMON_LOOKUP_TABLE NOT NULL VARCHAR2(30) COMMON_LOOKUP_COLUMN NOT NULL VARCHAR2(30) COMMON_LOOKUP_TYPE NOT NULL VARCHAR2(30) COMMON_LOOKUP_CODE VARCHAR2(8) COMMON_LOOKUP_MEANING NOT NULL VARCHAR2(255) CREATED_BY NOT NULL NUMBER CREATION_DATE NOT NULL DATE LAST_UPDATED_BY NOT NULL NUMBER LAST_UPDATE_DATE NOT NULL DATE You have two options when you query a common_lookup table. One is to read the rows one line at a time and the other read is to read all the rows through a BULK COLLECT operation. The article shows you both approaches. The first approach uses a line-by-line approach. It takes two mandatory parameters, which yields an empty web form. The third parameter is the lookup key, which would be a foreign key column value. The fourth parameter is an HTML class attribute value. The HTML class attribute would let you create floating menus. The following creates a working function that returns an OPTION tag list: SQL> CREATE OR REPLACE FUNCTION get_option_list 2 ( pv_table_name VARCHAR2 3 , pv_column_name VARCHAR2 4 , pv_lookup_key NUMBER := 0 5 , pv_class_name VARCHAR2 := NULL ) RETURN VARCHAR2 IS 6 7 /* Return HTML snippet. */ 8 lv_html VARCHAR2(4000); 9 10 /* Declare a dynamic cursor. */ 11 CURSOR cv_list 12 ( cv_table_name VARCHAR2 13 , cv_column_name VARCHAR2 ) IS 14 SELECT cl.common_lookup_id 15 , cl.common_lookup_type 16 , cl.common_lookup_meaning 17 FROM common_lookup cl 18 WHERE cl.common_lookup_table = cv_table_name 19 AND cl.common_lookup_column = cv_column_name 20 ORDER BY cl.common_lookup_meaning; 21 22 BEGIN 23 24 /* Set initial value when no foreign key exists. */ 25 IF pv_lookup_key = 0 THEN 26 lv_html := ' Select Type '; 28 ELSE 29 lv_html := ' Select Type '; 31 END IF; 32 33 FOR i IN cv_list(pv_table_name, pv_column_name) LOOP 34 /* Set subsequent value when foreign key is set. */ 35 IF pv_lookup_key = i.common_lookup_id THEN 36 lv_html := lv_html||' ' 38 || i.common_lookup_meaning||' '; 39 ELSE 40 lv_html := lv_html||' ' 42 || i.common_lookup_meaning||' '; 43 END IF; 44 END LOOP; 45 /* Return HTML snippet. */ 46 RETURN lv_html; 47 END get_option_list; 48 / The cursor on lines 11 through 20 uses the super key of the table and column name to return the unique set from the common_lookup table. The IF -block on lines 25 through 31 checks whether you sent a lookup key parameter. It sets the unselected value when as the selected value for display when you haven’t sent the lookup key. It alternatively unsets the unselected value when another value should be the selected value. The selected value in a SELECT tag is the one you see displayed without clicking it for options. You should note that lines 27 and 30 include ampersands (&). You need to set DEFINE to OFF before you try to compile the get_option_list function because that avoids threating these specialized HTML macros as substitution variables. The get_option_list function displays the following HTML snippet, which is artificially formatted across rows: Select Type American Express Card Discover Card Master Card VISA Card The VISA Card entry is highlighted, which means it will show as the selected value in a web form. You’ll see that example later in this article. Shifting gears, the next example replaces the row-by-row logic and uses a BULK COLLECT to populate the OPTION tags. It requires the setup of an SQL-level object type and a collection of the SQL-level object type. You create the SQL-level object type like this: SQL> CREATE OR REPLACE 2 TYPE lookup_object IS OBJECT 3 ( lookup_id NUMBER 4 , lookup_type VARCHAR2(30) 5 , lookup_value VARCHAR2(30)); 6 / Then, you create a table collection of the base object, like SQL> CREATE OR REPLACE 2 TYPE lookup_table IS TABLE OF lookup_object; 3 / The two SQL-level object types are needed to perform a BULK COLLECT . The BULK COLLECT reduces the IO reading the data by putting it in a table collection. You read the table collection in memory, which is slightly faster than reading it row-by-row. It’s only a slight difference because these are very small sets. Here one of the refactored elements of the get_option_list function: 10 /* Declare and construct an empty collection. */ 11 lv_lookup_table COMMON_LOOKUP_TABLE := common_lookup_table(); 12 13 /* Declare a dynamic cursor. */ 14 CURSOR cv_list 15 ( cv_table_name VARCHAR2 16 , cv_column_name VARCHAR2 ) IS 17 SELECT common_lookup_object( cl.common_lookup_id 18 , cl.common_lookup_type 19 , cl.common_lookup_meaning) 20 FROM common_lookup cl 21 WHERE cl.common_lookup_table = cv_table_name 22 AND cl.common_lookup_column = cv_column_name 23 ORDER BY cl.common_lookup_meaning; 24 25 BEGIN 26 /* Bulk open and assign values. */ 27 OPEN cv_list(pv_table_name, pv_column_name); 28 FETCH cv_list BULK COLLECT INTO lv_lookup_table; 29 CLOSE cv_list; Line 11 shows the creation of a local instance of the SQL-level table collection. You need it to assign a set of rows in a BULK COLLECT operation. Lines 17 through 19 show how you use the columns returned by the query to construct SQL-level object type instances. Lines 27 through 29 show the BULK COLLECT operation with a parameter-driven cursor. The next change involves how you read and translate the data into a collection. The excerpt from the function that performs that task is: 40 FOR i IN 1..lv_lookup_table.COUNT LOOP 41 /* Set subsequent value when foreign key is set. */ 42 IF pv_lookup_key = lv_lookup_table(i).common_lookup_id THEN 43 lv_html := lv_html||' '|| lv_lookup_table(i).common_lookup_meaning ||' '; 46 ELSE 47 lv_html := lv_html||' '|| lv_lookup_table(i).common_lookup_meaning ||' '; 50 END IF; 51 END LOOP; Line 40 shows you how to loop through a collection. Lines 42, 44, 45, 48, and 49 show you how to reference elements of the SQL-level collection. This function returns the same data set as before. This section has shown you how to translate relational data into an HTML OPTION list. The next section will show you how it makes leveraging foreign keys against a common_lookup table easy and effective. How to use an HTML fragment in a web form This part of the article shows you how to use the OPTION list function in a web form. It’s fair to say that both PL/SQL and HTML are verbose development languages. Many in the development community acknowledge PL/SQL as a proprietary programming language but they see HTML as a markup system to display text. You create an event driven programming language when you combine HTML and JavaScript. This web page only displays the form. The following is the code to display the form: SQL> CREATE OR REPLACE 2 PROCEDURE basic_form 3 ( first_name VARCHAR2 := NULL 4 , middle_name VARCHAR2 := NULL 5 , last_name VARCHAR2 := NULL 6 , account_number VARCHAR2 := NULL 7 , credit_card_number VARCHAR2 := NULL ) IS 8 9 /* Declare local variables. */ 10 lv_member_id NUMBER; 11 lv_member_table VARCHAR2(30) := 'MEMBER'; 12 lv_member_column1 VARCHAR2(30) := 'MEMBER_TYPE'; 13 lv_member_column2 VARCHAR2(30) := 'CREDIT_CARD_TYPE'; 14 lv_member_type NUMBER; 15 lv_contact_id NUMBER; 16 lv_contact_table VARCHAR2(30) := 'CONTACT'; 17 lv_contact_column VARCHAR2(30) := 'CONTACT_TYPE'; 18 lv_contact_type NUMBER; 19 20 /* Declare a local Cascading Style Sheet. */ 21 lv_css VARCHAR2(1400); 22 lv_out VARCHAR2(4000); 23 24 /* Declare a cursor. */ 25 CURSOR get_member 26 ( cv_first_name VARCHAR2 27 , cv_middle_name VARCHAR2 28 , cv_last_name VARCHAR2 29 , cv_account_number VARCHAR2 30 , cv_credit_card_number VARCHAR2 ) IS 31 SELECT m.account_number 32 , m.member_type 33 , m.credit_card_number 34 , m.credit_card_type 35 , c.first_name 36 , c.middle_name 37 , c.last_name 38 , c.contact_type 39 FROM member m INNER JOIN contact c 40 ON m.member_id = c.member_id 41 WHERE (NVL(c.first_name,'x') = NVL(cv_first_name,'x') 42 AND NVL(c.last_name,'x') = NVL(cv_last_name,'x')) 43 OR (NVL(c.first_name,'x') = NVL(cv_first_name,'x') 44 AND NVL(c.middle_name,'x') = NVL(cv_middle_name,'x') 45 AND NVL(c.last_name,'x') = NVL(cv_last_name,'x')) 46 OR m.account_number = cv_account_number 47 OR m.credit_card_number = cv_credit_card_number; 48 49 BEGIN 50 /* Assign the css to a local variable. */ 51 FOR i IN (SELECT css_text 52 FROM css 53 WHERE css_name = 'form-standard') LOOP 54 lv_css := i.css_text; 55 END LOOP; 56 57 /* Print header for form */ 58 htp.print(' '); 59 htp.print(lv_css); 60 htp.htmlopen; 61 htp.headopen; 62 htp.headclose; 63 htp.bodyopen; 64 65 /* Get dynamic data. */ 66 FOR i IN get_member( first_name 67 , middle_name 68 , last_name 69 , account_number 70 , credit_card_number) LOOP 71 72 /* Collect HTML snippet for basic form. */ 73 lv_out := ' '; 74 lv_out := lv_out || ' Membership Account Information '; 75 lv_out := lv_out || ' '; 76 lv_out := lv_out || ' '; 77 lv_out := lv_out || ' Account # '; 78 lv_out := lv_out || ' '; 79 lv_out := lv_out || ' '; 80 lv_out := lv_out || get_option_list(lv_member_table, lv_member_column1, i.member_type ); 81 lv_out := lv_out || ' '; 82 lv_out := lv_out || ' Credit Card # '; 83 lv_out := lv_out || ' '; 84 lv_out := lv_out || ' '; 85 lv_out := lv_out || get_option_list(lv_member_table, lv_member_column2, i.credit_card_type); 86 lv_out := lv_out || ' '; 87 lv_out := lv_out || ' '; 88 lv_out := lv_out || ' '; 89 lv_out := lv_out || ' '; 90 lv_out := lv_out || ' First Name '; 91 lv_out := lv_out || ' Middle Name '; 92 lv_out := lv_out || ' Last Name '; 93 lv_out := lv_out || ' Customer '; 94 lv_out := lv_out || ' '; 95 lv_out := lv_out || ' '; 96 lv_out := lv_out || ' '; 97 lv_out := lv_out || ' Type '; 98 lv_out := lv_out || ' '; 99 lv_out := lv_out || get_option_list(lv_contact_table, lv_contact_column, i.contact_type); 100 lv_out := lv_out || ' '; 101 lv_out := lv_out || ' '; 102 lv_out := lv_out || ' '; 103 lv_out := lv_out || ' '; 104 lv_out := lv_out || ' '; 105 lv_out := lv_out || ' '; 106 lv_out := lv_out || ' '; 107 END LOOP; 108 109 /* Print footer for form. */ 110 htp.print(lv_out); 111 htp.bodyclose; 112 htp.htmlclose; 113 114 END basic_form; 115 / Lines 41 through 47 uses a WHERE clause to enable the entry of first and last names, first, middle, and last names, account number, or credit card type to retrieve a valid row. A blank entry screen results when there are no matching criteria. Line 51 through 55 reads a CSS sheet into memory and assigns it to a local variable. Lines 66 through 70 send parameters into the cursor. Lines 80, 85, and 99 calls the get_option_list function and returns a specific OPTION list for any given foreign key value. Lines 73 through 106 assign raw HTML to a local variable. Line 110 effectively echoes the content to the web page. The basic_form web page displays the following dialog: You should note that the lookup values highlight the values associated with the foreign key values in the member and contact tables. If you click on any of the dropdown fields, the lookup shows the list of possible choices. The get_option_list function is a reusable library that lets you display any lookup in your web form. In the example above, the get_option_list returns three lookup sets. This article has shown you how to use lookup tables to create OPTION lists and how to use this type of function in a web form.
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