[bbk5141]第14集 Chapter 06 Working with Composite Data Types(Collection)

DECLARE
        SUBTYPE location_t IS VARCHAR2(64);
        TYPE population_type IS TABLE OF NUMBER INDEX BY location_t;

        l_country_population population_type;
        l_count PLS_INTEGER;
        l_location location_t;
BEGIN
        l_country_population('Greenland') := 100000;
        l_country_population('USA') := 300000000000;
        l_country_population('Icland') := 750000;
        l_country_population('Australia') := 23000000;
        l_country_population('usa') := 40000000;

        l_count := l_country_population.COUNT;
        DBMS_OUTPUT.PUT_LINE('COUNT = ' || l_count);

        l_location := l_country_population.FIRST;
        DBMS_OUTPUT.PUT_LINE('First Row = ' || l_location);
        DBMS_OUTPUT.PUT_LINE('First Value =' || l_country_population(l_location));

        l_location := l_country_population.LAST;
        DBMS_OUTPUT.PUT_LINE('Last Row = ' || l_location);
        DBMS_OUTPUT.PUT_LINE('Last Value =' || l_country_population(l_location));

END;
/

DECLARE
        TYPE population_type IS TABLE OF NUMBER INDEX BY VARCHAR2(64);

        city_population population_type;
        i VARCHAR2(64);
BEGIN
        city_population('Smallville') := 2000;
        city_population('Midland') := 750000;
        city_population('Megalopolis') := 1000000000;

        city_population('Smallville') := 2001;

        i := city_population.FIRST;
        DBMS_OUTPUT.PUT_LINE(i);

        WHILE(i IS NOT NULL)
        LOOP
                DBMS_OUTPUT.PUT_LINE('Key->' || i || ',Value ->' || city_population(i));
                i := city_population.NEXT(i);
        END LOOP;
END;
/

demo : lookup

DECLARE
        SUBTYPE name_t IS VARCHAR2(32);
        TYPE lookup_t IS TABLE OF name_t INDEX BY PLS_INTEGER;

        name_tab lookup_t;

        name name_t := 'Frank';
        l_index PLS_INTEGER;
        l_found BOOLEAN := FALSE;
BEGIN
        --Populate the lookup table first
        name_tab(0) := 'Wilson';
        name_tab(1) := 'Jim';
        name_tab(2) := 'Richard';
        name_tab(3) := 'Michael';
        name_tab(4) := 'Frank';
        name_tab(5) := 'Chris';
        name_tab(6) := 'Walnut';
        name_tab(7) := 'Patrick';
        name_tab(8) := 'Arcer';
        --Lookup the name in the lookup table
        l_index := name_tab.FIRST;
        WHILE l_index IS NOT NULL
        LOOP
                IF l_index IS NULL THEN
                        EXIT;
                END IF;

                IF name = name_tab(l_index) THEN
                        l_found := TRUE;
                        EXIT;
                END IF;

                l_index := name_tab.NEXT(l_index);

        END LOOP;

        IF l_found THEN
                DBMS_OUTPUT.PUT_LINE('I found it :' || l_index || '-->' || name);
        ELSE
                DBMS_OUTPUT.PUT_LINE('I cannot find it.Sorry!');
        END IF;
END;

/

改进版

DECLARE
        SUBTYPE name_t IS VARCHAR2(32);
        SUBTYPE value_t IS VARCHAR2(32);

        TYPE lookup_t IS TABLE OF value_t INDEX BY name_t;

        name_tab        lookup_t;

        name    name_t := 'Frank';

BEGIN
        --Populate the lookup table first
        name_tab('Wilson')      := 'a_Wilson';
        name_tab('Jim')         := 'b_Jim';
        name_tab('Richard')     := 'c_Richard';
        name_tab('Michael')     := 'd_Michael';
        name_tab('Frank')       := 'e_Frank';
        name_tab('Chris')       := 'f_Chris';
        name_tab('Walnut')      := 'g_Walnut';
        name_tab('Patrick')     := 'h_Patrick';
        name_tab('Arcer')       := 'i_Arcer';
        --Lookup the name in the lookup table
        IF name_tab.EXISTS(name) THEN
                DBMS_OUTPUT.PUT_LINE('I found it ! =>' || name || '->' || name_tab(name));
        ELSE
                DBMS_OUTPUT.PUT_LINE('Sorry,I cannot find it!');
        END IF;
END;

/

Hash Functions

Index By Integer or String ?

Performance about Index by String