Usage methods and cases of PLSQL blocks, cursors, functions, stored procedures and triggers of Oracle Database

One ,PL SQL

1） Introduce

  PL/SQL Block is in sql An application developed on the basis of language in a sentence , It can deal with all kinds of complex SQL operation .

Sentence format ：

DECLARE：
	 Declaration part 
BEGIN
	 Write a topic 
EXCEPTION
	 Capture exception 
END
/

2）do…while loop

  PL/SQL It also includes ： loop 、 Conditional control statements such as branches .

Sentence format ：

LOOP
	 A circular statement 
EXIT WHEN  Termination conditions 
	 The loop condition must be changed 
END LOOP ;

Cyclic output 1~10：

DECLARE
    cou NUMBER ;
BEGIN
    --  You must give an initial value 
    cou := 1;
    LOOP
        DBMS_OUTPUT.put_line('cou = ' || cou);
        EXIT WHEN cou > 10;
        cou := cou + 1;
    END LOOP;
END ;
/
-- This loop will be executed once before the loop 

3）while loop

Format ：

while( Judge the conditions of the cycle ) loop
	 A circular statement ;
	 Changes in cycle conditions ;
END loop;

Cyclic output 1~10：

DECLARE
    cou NUMBER ;
BEGIN
    --  You must give an initial value 
    cou := 1;
    WHILE(cou < 10) LOOP
        DBMS_OUTPUT.put_line('cou = ' || cou);
        cou := cou + 1;
    END LOOP;
END;
/
-- This loop will judge before executing the statement 

4）for loop

Format ：

FOR  Variable name  in  The initial value of the variable .. End value  lOOP
	 Loop statement ;
END loop;

Cyclic output 1~10：

DECLARE
    cou NUMBER ;
BEGIN
	-- This statement will automatically 1 To 10 Assign a value to cou
    FOR cou in 1..10 loop
        DBMS_OUTPUT.put_line('cou = ' || cou);
    END LOOP;
END ;
/

5）if conditional

Format ：

IF  Conditions  THEN
	 When conditions are met ,  Execute this statement 
END IF;

Case study ：

DECLARE
    cou NUMBER ;
BEGIN
    cou := 11;
    IF cou > 10 THEN
        DBMS_OUTPUT.put_line('cou = ' || cou);
    end if;
END ;
/
-- Output 11

6）if…else conditional

Format ：

IF  Conditions  THEN
	 When conditions are met ,  Execute this statement 
END IF;

Case study ：

DECLARE
    cou NUMBER ;
BEGIN
    cou := 8;
    IF cou > 10 THEN
        DBMS_OUTPUT.put_line('cou = ' || cou);
    ELSE
        DBMS_OUTPUT.put_line('cou = ' || cou);
    end if;
END ;
/
-- Output 8

7）if…elsif…else conditional

Format ：

IF  Conditions  THEN
	 When conditions are met ,  Execute this statement 
ELSIF  Conditions  THEN
	 When this condition is met , Execute this statement 
ELSE
END IF;

Case study ：

DECLARE
    cou NUMBER ;
BEGIN
    cou := 8;
    IF cou > 10 THEN
        DBMS_OUTPUT.put_line('cou = ' || cou);
    ELSIF cou < 5 THEN
        DBMS_OUTPUT.put_line('cou = ' || cou);
    ELSE
        DBMS_OUTPUT.put_line('cou = ' || cou);
    end if;
END ;
/
-- Output 8

8）GOTO sentence

Format ：

IF  Conditions  THEN
	 When conditions are met ,  Execute this statement 
ELSIF  Conditions  THEN
	 When this condition is met , Execute this statement 
ELSE
END IF;

Case study ：

DECLARE
    emo EMPLOYEE.EMP00%TYPE;
    name EMPLOYEE.EMP01%TYPE;
BEGIN
    emo := '70443BA4-7174-46CC-8A7D-6DA04627B770';
    SELECT EMP01 INTO name FROM EMPLOYEE WHERE EMP00 = emo;
    IF name=' Zhou Kang ' THEN
        GOTO po1;
    ELSIF name=' Bai an ' THEN
        GOTO po2;
    ELSE
        GOTO po3;
    end if;

    <<po1>>
    DBMS_OUTPUT.put_line('po1');
    <<po2>>
    DBMS_OUTPUT.put_line('po2');
    <<po3>>
    DBMS_OUTPUT.put_line('po3');
END ;
/

Two , The cursor 、 function

1） The cursor

   A cursor is a kind of PL/SQL Control structure , It can be done to SQL Statement processing for display control , It is convenient to process the row data of the table one by one . A cursor is not a database object , Just stored in memory .

Operation steps ：

• declare cursor
• Open cursor
• Take out the results , At this time, the result is a whole row of data
• Close cursor
• Use ROWTYPE type , This type indicates that a whole row of data can be loaded in

DECLARE
    emp EMPLOYEE.EMP00%TYPE; -- Define a parameter 
    empInfo EMPLOYEE%rowtype; -- Define a rowType,  Used to hold a whole row of data 
BEGIN
    emp := '7350F9DE-F5BC-461A-B499-F86680D2DA4E';
    SELECT * INTO empInfo FROM EMPLOYEE WHERE EMP00 = emp;
    DBMS_OUTPUT.PUT_LINE(' full name =' || empInfo.EMP01); -- Can pass emoInfo.  To access all the fields in this row 
end;

2） Use for Loop operation cursor （ Commonly used ）

DECLARE
    CURSOR mycur IS SELECT * FROM EMPLOYEE; --List(EMPLOYEE)
    empInfo EMPLOYEE%rowtype;
BEGIN
    -- Cursor operations use loops ,  But the cursor must be opened before operation 
    OPEN mycur;
    -- Move the cursor down one line 
    FETCH mycur INTO empInfo;
    -- Determine whether there is any data found in this line 
        WHILE (mycur%FOUND) LOOP
            DBMS_OUTPUT.put_line(' full name =' || empInfo.EMP01);
            -- Modify the cursor 
            FETCH mycur INTO empInfo;
        end loop;
end;
/
-- The names of all the people in the table are output 

3） Cursor case exercise

   Now we need to raise wages for employees in all departments , Raise wages according to their department , The following rules ：

• 10 The sector rose 10%
• 20 The sector rose 20%
• 30 The sector rose 30%
• The salary increase of employees in all departments can not exceed 5k, If it exceeds, press 5k Calculation .

DECLARE
    cursor mycur is SELECT * FROM emp;
    empInfo emp%rowtype;
    s emp.sal%TYPE;
BEGIN
    for empInfo in mycur loop
        if empInfo.deptno = 10 then
            s := empInfo.sal * 1.1;
        elsif empInfo.deptno = 20 then
            s := empInfo.sal * 1.2;
        elsif empInfo.deptno = 30 then
            s := empInfo.sal * 1.3;
        end if;

        if s > 5000 then
            s = 5000;
        end if;
        
        UPDATE emp SET sal = s WHERE emp00 = empInfo.emp00;
    end loop;
end;
/

4） function

   A function is a process with a return value . Define a function , This function can find out the current position of the employee according to the transferred employee number .

CREATE OR REPLACE FUNCTION "function"(emp IN varchar2) RETURN VARCHAR2
AS
    DMCPT VARCHAR2(1024);
BEGIN
    SELECT DMCPT INTO DMCPT FROM EMPLOYEE LEFT JOIN DM07 ON EMPLOYEE.EMP11 = DM07.DMCOD WHERE EMP00 = emp;
    RETURN DMCPT;
end;
/

SELECT "function"('7350F9DE-F5BC-461A-B499-F86680D2DA4E') FROM DUAL;

   Function can be used to handle some complex logical business , It's equivalent to using the code sql Write it out in a way , At the same time, some general conversion formats and other codes can also be abstracted into a function . May refer to ： Function that returns the time difference between the specified date and the current date

3、 ... and , stored procedure

   Compared with the process , A stored procedure is a procedure that exists in a database object . If the compilation is wrong , It can be used show errors or show errors procedure myproc.

Define a simple stored procedure ：

CREATE OR REPLACE PROCEDURE myproc1 --PROCEDURE n. The process ,  Program 
AS
    i NUMBER;
    BEGIN
        i := 100;
        DBMS_OUTPUT.PUT_LINE('i=' || i); -- Calling stored procedure ,  Direct output 100
    END;
/

   If it's a command line window ,exec myproc1 You can call the stored procedure , If it is sql Under the window, you need to use PLSQL sentence

DECLARE
	 Defining parameters ;
BEGIN
	myproc1; -- If the stored procedure has parameters ,  You need to pass parameters 
END;

Write a stored procedure , The number of the person can be passed in 、 full name 、 Gender （0,1 Instead of ）, After this stored procedure is invoked, the additional operation of personnel can be completed. .

CREATE OR REPLACE PROCEDURE myproc2(ENO EMPLOYEE.EMP00%TYPE, NAME EMPLOYEE.EMP01%TYPE, XB EMPLOYEE.EMP02%TYPE)
AS
    cou NUMBER;
    BEGIN
        -- First, judge whether the number is used ,  If used, you cannot add 
        SELECT COUNT(EMP00) INTO cou FROM EMPLOYEE WHERE EMP00 = ENO;
        IF cou = 0 THEN
            -- You can add 
            INSERT INTO EMPLOYEE(EMP00, EMP01, EMP02) VALUES (ENO, NAME, XB);
            DBMS_OUTPUT.PUT_LINE(' Personnel inserted successfully !');
        ELSE
            DBMS_OUTPUT.PUT_LINE(' This person number already exists ,  Can't insert !');
        END IF;
    END;
/

begin
  myproc2('7350F9DE-F5BC-461A-B499-F86680D2DA4F', ' Yin yang man ', '1');
end;

Parameter types of stored procedures , Add... When specifying the parameter type , similar myproc2(ENO IN OUT EMPLOYEE.EMP00%TYPE)：

• IN： Value passed , The default value is
• IN OUT： Bring value into , Bring out the value
• OUT： Bring no value into , Bring out the value

Delete stored procedure ：

DROP PROCEDURE myproc2;

Four , trigger

   Stored in a database , And implicitly executed stored procedure . stay Oracle 8i Before , Only tables and views are allowed DML operation , from 8i after , Not only can it support DML trigger , It is also allowed to give system events and DDL The operation of .

1） Statement triggers

• BEFORE Statement triggers , You can control the of the table INSERT OR UPDATE OR DELETE Filter before operation ：

-- It is forbidden to change employee information on rest days 
CREATE OR REPLACE TRIGGER TR_SRC_EMP --TRIGGER n. trigger 
    BEFORE INSERT OR UPDATE OR DELETE
    ON EMP
BEGIN
    IF TO_CHAR(SYSDATE, 'DY', 'NLS_DATE_LANGUAGE=AMERICAN') IN ('SAT', 'SUN') THEN
        RAISE_APPLICATION_ERROR(-20001, 'CAN‟T MODIFY USER INFORMATION IN WEEKEND');
    END IF;
END;
/

-- You can listen to the type of operation here 
CREATE OR REPLACE TRIGGER TR_SRC_EMP
    BEFORE INSERT OR UPDATE OR DELETE
    ON EMP
BEGIN
    IF TO_CHAR(SYSDATE, 'DY') IN (' Saturday ', ' Sunday ') THEN
        CASE
            WHEN INSERTING THEN
                RAISE_APPLICATION_ERROR(-20001, 'FAIL TO INSERT');
            WHEN UPDATING THEN
                RAISE_APPLICATION_ERROR(-20001, 'FAIL TO UPDATE');
            WHEN DELETING THEN
                RAISE_APPLICATION_ERROR(-20001, 'FAIL TO DELETE');
            END CASE;
    END IF;
END;
/

• AFTER Statement triggers , Operations after adding, deleting, and modifying tables ：

-- For statistics in EMP Added in the table 、 Delete 、 Number of changes , Create a statistical table 
CREATE TABLE AUDIT_TABLE
(
    NAME      VARCHAR2(20),
    INS       INT,
    UPD       INT,
    DEL       INT,
    STARTTIME DATE,
    ENDTIME   DATE
);

-- Set up triggers ,  The number of additions, deletions and modifications is classified 
CREATE OR REPLACE TRIGGER TR_AUDIT_EMP
    AFTER INSERT OR UPDATE OR DELETE
    ON EMP
DECLARE
    V_TEMP INT;
BEGIN
    SELECT COUNT(*) INTO V_TEMP FROM AUDIT_TABLE WHERE NAME ='EMP';
    IF V_TEMP = 0 THEN
        INSERT INTO AUDIT_TABLE VALUES ('EMP', 0, 0, 0, SYSDATE, NULL); -- without EMP The record of the table ,  Then build a new one 
    END IF;
    CASE
        WHEN INSERTING THEN
            UPDATE AUDIT_TABLE SET INS=INS + 1, ENDTIME=SYSDATE WHERE NAME = 'EMP'; -- If it's a new operation ,  will INS+1,  The same goes for other types 
        WHEN UPDATING THEN
            UPDATE AUDIT_TABLE SET UPD=UPD + 1, ENDTIME=SYSDATE WHERE NAME = 'EMP';
        WHEN DELETING THEN
            UPDATE AUDIT_TABLE SET DEL= DEL + 1, ENDTIME=SYSDATE WHERE NAME = 'EMP';
        END CASE;
END;
/

2） Row trigger , perform DML In operation , Trigger is triggered once for each line of action

• BEFORE Row trigger

-- When updating employee salaries ,  The new salary cannot be lower than the original salary 
CREATE OR REPLACE TRIGGER TR_EMP_SAL
    BEFORE UPDATE OF SAL -- Update trigger of salary field 
    ON EMP
    FOR EACH ROW -- Create row triggers for each row 
BEGIN
    IF :NEW.SAL < :OLD.SAL THEN -- If the new salary is less than the old salary 
        RAISE_APPLICATION_ERROR(-20010, 'SAL SHOULD NOT BE LESS');
    END IF;
END;
/

• AFTER Row trigger

-- Create a new process table ,  Count the salary changes of employees 
CREATE TABLE AUDIT_EMP_CHANGE
(
    NAME   VARCHAR2(10),
    OLDSAL NUMBER(6, 2),
    NEWSAL NUMBER(6, 2),
    TIME   DATE
);

-- Set up triggers ,  Statistics of employee salary changes 
CREATE OR REPLACE TRIGGER TR_SAL_SAL
    AFTER UPDATE OF SAL -- Triggered after salary update 
    ON EMP
    FOR EACH ROW
DECLARE
    V_TEMP INT;
BEGIN
    SELECT COUNT(*) INTO V_TEMP FROM AUDIT_EMP_CHANGE WHERE NAME = :OLD.ENAME;
    IF V_TEMP = 0 THEN
        INSERT INTO AUDIT_EMP_CHANGE VALUES (:OLD.ENAME, :OLD.SAL, :NEW.SAL, SYSDATE);
    ELSE
        UPDATE AUDIT_EMP_CHANGE
        SET OLDSAL=:OLD.SAL,
            NEWSAL=:NEW.SAL,
            TIME=SYSDATE
        WHERE NAME = :OLD.ENAME;
    END IF;
END;
/

Add trigger row limit ：

CREATE OR REPLACE TRIGGER TR_SAL_SAL
    AFTER UPDATE OF SAL
    ON EMP
    FOR EACH ROW
    WHEN (OLD.JOB ='SALESMAN') -- Only when employees JOB='SALESMAN'  when ,  This trigger is triggered only when the salary is updated 
DECLARE
    V_TEMP INT;
BEGIN
    SELECT COUNT(*) INTO V_TEMP FROM AUDIT_EMP_CHANGE WHERE NAME = :OLD.ENAME;
    IF V_TEMP = 0 THEN
        INSERT INTO AUDIT_EMP_CHANGE VALUES (:OLD.ENAME, :OLD.SAL, :NEW.SAL, SYSDATE);
    ELSE
        UPDATE AUDIT_EMP_CHANGE
        SET OLDSAL=:OLD.SAL,
            NEWSAL=:NEW.SAL,
            TIME=SYSDATE
        WHERE NAME = :OLD.ENAME;
    END IF;
END;
/

3） Trigger notes

   To write DML Trigger time , Trigger code cannot read data from the base table corresponding to the trigger .

If based on EMP Table creation trigger , Then the execution code of the trigger cannot contain pairs EMP Table query operation .

CREATE OR REPLACE TRIGGER TR_EMP_SAL
    BEFORE UPDATE OF EMP01
    ON EMPLOYEE
    FOR EACH ROW
DECLARE
    NAME VARCHAR2(8);
BEGIN
    SELECT EMP01 INTO NAME FROM EMPLOYEE;
    IF :NEW.EMP01 = NAME THEN
        RAISE_APPLICATION_ERROR(-21000, 'ERROR');
    END IF;
END;
/

-- No error will be reported when creating ,  But updating the table data will report an error 
UPDATE EMPLOYEE SET EMP01=' Zhou Kang ' WHERE EMP00 = '7350F9DE-F5BC-461A-B499-F86680D2DA4E';

4） System event triggers

   Triggers can help us do some data verification 、 Data recording, etc , stay Oracle Some system event triggers are built-in , be based on Oracle System events for （LOGON,STARTUP） The trigger created . By using system triggers , Provides a mechanism for tracking system or database changes , Some built-in system triggers are as follows ：

Trigger Name	purpose
ORA_CLIENT_IP_ADDRESS	Used to return to the client IP Address
ORA_DATABASE_NAME	Used to return the current database name
ORA_DES_ENCRYPTED_PASSWORD	For return DES Encrypted user password
ORA_DICT_OBJ_NAME	For return DDL The database object name corresponding to the operation
ORA_DICT_OBJ_NAME_LIST(NAME_LIST OUT ORA_NAME_LIST_T)	Used to return the list of object names modified in the event
ORA_DICT_OBJ_OWNER	For return DDL The owner name of the object corresponding to the operation
ORA_DICT_OBJ_OWNER_LIST(OWNER_LIST OUT ORA_NAME_LIST_T)	Used to return the owner list of the object modified in the event
ORA_DICT_OBJ_TYPE	For return DDL The type of data object corresponding to the operation
ORA_GRANTEE(USER_LIST OUT ORA_NAME_LIST_T)	Used to return the authorizer of the authorization event
ORA_INSTANCE_NUM	Used to return routine number
ORA_IS_ALTER_COLUMN(COLUMN_NAME IN VARCHAR2)	Used to detect whether a specific column has been modified
ORA_IS_CREATING_NESTED_TABLE	Used to detect whether nested tables are being built
ORA_IS_DROP_COLUMN(COLUMN_NAME IN VARCHAR2)	Used to detect whether a specific column has been deleted
ORA_IS_SERVERERROR(ERROR_NUMBER)	Used to detect whether a specific... Is returned Oracle error
ORA_LOGIN_USER	Used to return the login user name
ORA_SYSEVENT	Used to return the name of the system event that triggered the trigger

5） Establish system event trigger

   With the above system event trigger , You can create some special triggers .

• Log user login and logout events , Login and exit triggers can be established respectively ：

-- Establish login and exit information table 
CREATE TABLE log_table
(
    USERNAME    VARCHAR2(20),
    LOGON_TIME  DATE,
    LOGOFF_TIME DATE,
    ADDRESS     VARCHAR2(20)
);

Established LOG_TABLE After the table , You can create triggers to operate on this table , Login trigger and exit trigger must be established with privileged user identity , And the login trigger can only use AFTER keyword , The exit trigger can only use BEFORE keyword ：

CREATE OR REPLACE TRIGGER tr_logon
    AFTER LOGON ON DATABASE
    BEGIN
        INSERT INTO LOG_TABLE(USERNAME, LOGON_TIME, ADDRESS)
            VALUES(ORA_LOGIN_USER, SYSDATE, ORA_CLIENT_IP_ADDRESS);
    END;
/

CREATE OR REPLACE TRIGGER tr_logoff
    BEFORE LOGOFF ON DATABASE
    BEGIN
        INSERT INTO LOG_TABLE(USERNAME, LOGOFF_TIME, ADDRESS)
            VALUES(ORA_LOGIN_USER, SYSDATE, ORA_CLIENT_IP_ADDRESS);
    END;
/

• DDL trigger , In order to record what happened to the system DDL event （create、alter、drop） etc. , Can be established DDL trigger , First, establish a storage system DDL Tables of information ：

CREATE TABLE EVENT_DDL
(
    EVENT    VARCHAR2(20),
    USERNAME VARCHAR2(20),
    OWNER    VARCHAR2(10),
    OBJNAME  VARCHAR2(20),
    OBJTYPE  VARCHAR2(10),
    TIME     DATE
);

Set up triggers , Use AFTER keyword , Record what happened in the table DDL operation ：

CREATE OR REPLACE TRIGGER tr_ddl
    AFTER DDL ON SCHEMA
    BEGIN
        INSERT INTO event_ddl1 VALUES (ORA_SYSEVENT, ORA_LOGIN_USER, ORA_DICT_OBJ_OWNER, ORA_DICT_OBJ_NAME, ORA_DICT_OBJ_TYPE, SYSDATE);
    END;
/

DROP TABLE TEST;

6） Manage triggers

• See all triggers

SELECT TRIGGER_NAME, STATUS FROM USER_TRIGGERS;

• Disable triggers , Disable trigger means to disable the trigger temporarily , When the trigger is in ENABLE In the state of , If you execute on the table DML operation , The corresponding trigger will be triggered . If based on INSERT The operation establishes a trigger , When using SQL*Loader When loading large amounts of data , In order to speed up efficiency , Triggers should be temporarily disabled ：

ALTER TRIGGER TR_CHECK_SAL DISABLE;

• Activate trigger

ALTER TRIGGER TR_CHECK_SAL ENABLE;

• Batch prohibition 、 Activate trigger

ALTER TABLE EMPLOYEE DISABLE ALL TRIGGERS; -- Batch operation of all triggers in a table 
ALTER TABLE EMPLOYEE ENABLE ALL TRIGGERS;

• Recompile trigger , When using ALTER TABLE Command to modify table structure （ Add or delete columns ） when , Will turn its trigger into INVALID state , In this case , In order for the trigger to continue to work , Trigger needs to be recompiled ：

ALTER TRIGGER TR_DDL COMPILE;

• Delete trigger

DROP TRIGGER TR_EMP_SAL;