pl / sql-- basic syntax and operation

A: plsql total summarized as

. 1 .pl / SQL basic syntax structure 
　　DECLARE, the begin , Exception , End,: =, =, and other key character
 2 recording type ... type. IS Record (,,); (corresponding to the member variable java)
 3 flow control
        3.1 condition determining (two kinds) 
           Method 1: IF ... the then ... ... ELSIF the then ... the else ... End  IF ; 
           Second way: Case ... When ... the then .. . End ;
        3.2 loop structure (three kinds) 
           Method 1: loop ... Exit  When ...End Loop; 
           Second way: the while ... End Loop; 
           Three ways: for I in ... ... Loop End Loop;
        3.3 keyword
            goto out of the loop corresponds to the Java ( BREAK )
            Exit Exit
 4 cursor used (similar. iterator in the java iterators for traversing a set of)
 5 exception handling (three ways). 



6 storage.
        6 .1 stored function: return value
        6 .2 stored procedure: no return value 

7 flip-flop 

8 index 

9 . view

Two: declare variables with

  1 specify the type declaration, and a length (same type and table type, length to be greater than or equal table field length). 
    
  V_sal Number ( 10 , 2 ); 
  v_email VARCHAR2 ( 20 is ); 
  v_hire_date DATE; 
  
  2 . Directly field in a table the property assigned to the variable (recommended), less error-prone 

  v_sal employees.salary % type; 
  v_email employees.email % type; 
  v_hire_date employees.hire_date % type;

III. Record Type Definition Record (java in the subject)

 1 . Declared a class member behind the note record type with a comma, the last one without comma semicolon in parentheses following 
  type emp_record IS Record ( 
    v_sal employees.salary % type, 
    v_email employees.email % type, 
    v_hire_date employees.hire_date % type 
  ) ; 
  - the definition of a record type of the member variable 
  v_emp_record emp_record; - the back can be used directly v_emp_record variable name called. 
examples: dbms_output.put_line ( ' wage ' || v_emp_record.v_sal || ' , the message ' || v_emp_record.v_email | | ' , the date ' || v_emp_record.v_hire_date);

2 . Directly create a record type table   % ROWTYPE (recommended) 
  in the table all the fields and their types are declared to record this type, in order to call back 
  v_emp_record the Employees % ROWTYPE; 

examples: DBMS_OUTPUT.PUT_LINE ( ' salary ' || v_emp_record.salary || ' , the message ' || v_emp_record.email || ' , date ' || v_emp_record.hire_date);

Four: Assignment Problem: = and =

DECLARE 
  v_emp_id Number (10); 
the begin 
  v_emp_id : = 123; 
  Update the Employees 
  SET the salary = the salary + 100 
  WHERE the employee_id = v_emp_id; 
  DBMS_OUTPUT.PUT_LINE ( 'executed successfully'); 
End; - with a variable assignment: = 
--sql inside Assignment a = 
--plsq with equal function determines =

Five: conditional statement (two kinds) (recommended if..else) can handle a variety of conditions to determine, case not

1.if ... then ... elsif ... then ... else ... end if;

- Requirements: 150 Query the number of employees wages, salaries if it is greater than or equal to 10,000 print 'the salary> = 10000'; 
- if between 5,000 to 10,000, the print '5000 <= salary <10000' ; otherwise, print 'the salary <5000' 
DECLARE 
  v_sal employees.salary% type; - record table structure type 
  v_temp VARCHAR2 ( 50 );
 the begin 
  SELECT the salary INTO v_sal
   from the Employees WHERE the employee_id = 150 ; 

  IF v_sal > = 10000 
     the then v_temp: =  ' the salary> 10000 = ' ; 
  ELSIF v_sal > = 5000 
     the thenv_temp: =  ' 5000 <= the salary <10000 ' ;
   the else 
     v_temp: =  ' the salary <5000 ' ;
   End  IF ; 
  DBMS_OUTPUT.PUT_LINE ( ' real wage: ' || v_sal ||   ' , the output information: ' || v_temp) ;
 End ;

2.case ... when ... then ... end;

(1) number of digital case

- Requirements: 150 Query the number of employees wages, salaries if it is greater than or equal to 10,000 print 'the salary> = 10000'; 
- if between 5,000 to 10,000, the print '5000 <= salary <10000' ; otherwise, print 'the salary <5000' 
DECLARE 
  v_sal employees.salary % type; 
  v_temp VARCHAR2 ( 50 );
 the begin 
  SELECT the salary INTO v_sal
   from the Employees WHERE the employee_id = 150 ; 
   v_temp: = 
   Case the trunc (v_sal / 5000 ) When  0  the then   ' the salary> = 10000 ' 
                          When  . 1 the then   ' 5000 <= the salary <10000 ' 
                          the else   ' the salary <5000 ' 
   End ; 
   DBMS_OUTPUT.PUT_LINE ( ' real wage: ' || v_sal ||   ' , the output information: ' || v_temp);
 End ;

(2) varchar2 string case

- Requirements: 122 check out JOB_ID employees, if a value of 'IT_PROG', print 'the GRADE: A'; 
- 'AC_MGT', print 'GRADE B', 'AC_ACCOUNT' , print 'GRADE C'; otherwise the print 'the GRADE D' 
DECLARE 
  v_job_id employees.job_id % type; 
  v_temp VARCHAR2 ( 20 is );
 the begin 
  SELECT the job_id INTO v_job_id
   from the Employees WHERE the employee_id = 122 ; 
  v_temp: = 
  Case v_job_id When  ' IT_PROG '  the then  ' the GRADE: A ' 
                When  'AC_MGT' then 'GRADE B'
                when 'AC_ACCOUNT' then 'GRADE C'
                else 'GRADE D'
  end;
  DBMS_OUTPUT.put_line('job_id:'||v_job_id||' 打印信息:  '||v_temp);
end;

Six: loop structure (three kinds)

pl / sql-- basic syntax and operation

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