Basic grammar
[declare
— Definition]
begin
— Execution
[exception
— Exception handling part]
end;
Where, the definition section begins with DECLARE, which is optional; The execution section begins with BEGIN, which is required
The exception section starts with Exception, which is optional. End is the end tag of a PL/SQL block.
Note that I am using SQL Plus installed with Oracle. Note the first line. Otherwise, the console does not output.
When finished, type/and press Enter.
Common variable types
char() varchar2() number() date;
Operators and expressions
If branch statement
If conditions then
Execute statement;
Elsif conditions then
Execute statement;
else
Execute statement;
end if;
“Then” is the same as if else if else in Java. Looks so disgusting syntax) remember end if; At the end
Remember to use “THEN” for all branches except else
A case statement
The case condition
When value then executes the statement
When value then executes the statement
.
Else execution statement
end;
Case can have a return value.
Assign the result of case to B; However, if we make case have a return value, it cannot be end case after the end of the case statement; It can only be end;
Looping statements
The basic cycle
loop
The executive body
Exit when condition;
end loop;
Attention! This way of writing it, the executor will definitely execute it once. The condition in exit is to stop the loop.
The program is executed from the top down.
The while loop
Conditions of the while loop
The loop body
end loop;
The for loop
For is assigned to in [reverse] start.. The end of the loop
The loop body
end loop;
You can see that the order in which the for loop is executed determines the start and end conditions. Satisfies assignment to i. Executes the body of the loop and then evaluates again.
The I in the for loop can be undeclared. Start and end conditions can also be variables, but only of type number
But if the assigned variable does not exist. You cannot use the variable after the loop call ends.
Reverse does ++ to —
Goto statement A very destructive statement
Goto jumps to the defined tag. Set the symbol of the tag to << tag >>
null
Null is very special. First, two null’s are not equal. Null itself is not equal to null
The composite variable
A standard variable can only hold a single value, and its counterpart is a compound variable. Compound variables can combine multiple values of different data types
Stored in the same cell.
% type variable
This variable is of indefinite type. The exact type of a variable is the same as the type of the table field assigned to it.
Use the SELECT INTO statement to assign the queried value to a variable; But be careful with the %type assignment
You must ensure that the assignment results in a single row and column.
The % rowtype variable
% rowType declares a variable representing a row of records (an object) to which you assign a table data structure to variable X
