I'm trying to create a trigger in which, only under certain circumstances, an insert is performed on another table. Consider the following code:
create table journal (
pk integer primary key autoincrement,
dsc varchar(10) not null
);
create table users (
name varchar(30) primary key not null
);
create trigger users_ai
after insert on users
begin
select
case
when 1 then
insert into journal(dsc) values('foo')
end;
end;
I get the following error when I run this code:
Error: near line 10: near "insert": syntax error
In production, the "1" in the when clause would be replaced by a more complex expression. I've also tried "true" and get the same results. I've also tried surrounding the insert statement in parens and get the same results. Any ideas how to accomplish what I want?
If you look at the syntax diagram for "CREATE TRIGGER", you'll see your attempt just doesn't match. You can, however, simply use the WHEN branch (without needing FOR EACH ROW):
create trigger users_ai
after insert on users
when 1 begin
insert into journal(dsc) values('foo');
end;
OK, figured it out. Instead of putting a conditional expression in the block of the trigger, I used a when clause. Here's the code that works:
create trigger users_ai
after insert on users when 1
begin
insert into journal(dsc) values('foo');
end;
If that when expression is changed to something that returns false (say 0) then the insert isn't done. In production, the expression will sometimes return true, sometimes false, which, of course, is the point of this code. Thanks everybody!
I think that you want a CASE statement, not a CASE expression.
create trigger users_ai after insert on users
begin
case
when ... then insert into journal(dsc) values('foo');
when ... then ...;
else ...;
end case;
end;
Note: if your trigger needs access to the data that was just inserted, its definition should the for each row option.
You can try to use an INSERT ... SELECT and your expression in the WHERE clause.
...
INSERT INTO journal
(dsc)
SELECT 'foo'
WHERE 1 = 1;
...
1 = 1 needs to be replaced by your Boolean expression.
Related
i have a pl/sql procedure to modify/delete records based on a checkbox selection in my Apex application:
delete from s_objectif_operation where id_operation=:p124_id_operation;
for a in (select distinct id from s_objectif
where id in (
SELECT trim(regexp_substr(:P124_S_OBJECTIF, '[^:]+', 1, LEVEL)) str
FROM dual
CONNECT BY instr(:P124_S_OBJECTIF, ':', 1, LEVEL - 1) > 0
))
loop
insert into s_objectif_operation
(id_s_objectif, id_operation)
values
(a.id, :p124_id_operation);
end loop;
for every modification, this procedure deletes all the records and insert the correct ones back so i had to remove the "cascade on delete" option the foreign key constraint to suspend any child record removal but now the procedure is not working.
maybe "raise an exception" can work?
There is no need to delete all the records and re-inserting only the checked ones. That is a brute force approach and it works but it does not capture the real user action.
As an alternative you can just delete/insert the changes. To do that, create an additional page item P124_S_OBJECTIF_OLD and set it to the value P124_S_OBJECTIF with a computation after header (or any pre-rendering processing point after P124_S_OBJECTIF has been initialized). In your pl/sql code use APEX_STRING.SPLIT to process the checkbox values and the MULTISET operator to decide which values have been touched.
Then your pl/sql process code could look like this.
DECLARE
l_objectif_old apex_t_varchar2;
l_objectif_new apex_t_varchar2;
l_objectifs_added apex_t_varchar2;
l_objectifs_removed apex_t_varchar2;
BEGIN
l_objectif_old := apex_string.split(:P124_S_OBJECTIF_OLD,':');
l_objectif_new := apex_string.split(:P124_S_OBJECTIF,':');
l_objectifs_added := l_objectif_new MULTISET EXCEPT l_objectif_old;
l_objectifs_removed := l_objectif_old MULTISET EXCEPT l_objectif_new;
-- add new
FOR i IN 1 .. l_objectifs_added.COUNT LOOP
INSERT INTO s_objectif_operation (id_s_objectif, id_operation)
VALUES (l_objectifs_added(i), :P124_ID_OPERATION);
END LOOP;
-- delete old
FOR i IN 1 .. l_objectifs_removed.COUNT LOOP
BEGIN
DELETE FROM s_objectif_operation
WHERE id = l_objectifs_removed(i);
EXCEPTION WHEN OTHERS THEN
-- this will fire if there are child records. Add your own code.
NULL;
END;
END LOOP;
END;
Note that you might have to tweak the insert and delete statement to match your data structure.
I have set my column to int not null default 1... but whenever I save my record, it sets default value for that record to be 0.
I am not setting it anywhere. I don't know where I am making a mistake.
I have debugged my code , and when I am passing new entity object it is setting default value for not null to 0 .May be it is something with LINQ, But I don't know how to handle it.I don't want to explicitly assign value.
Thanks!
For sql-server, you can use SQL Server Profiler to catch all the scripts you run into the DB.
This may show you some details
Try running this query, replacing the 'myTable' and 'myColumn' values with your actual TABLE and COLUMN names, and see what's returned:
SELECT
OBJECT_NAME(C.object_id) AS [Table Name]
,C.Name AS [Column Name]
,DC.Name AS [Constraint Name]
,DC.Type_Desc AS [Constraint Type]
,DC.Definition AS [Default Value]
FROM sys.default_constraints DC
INNER JOIN sys.Columns C
ON DC.parent_column_id = C.column_id
AND DC.parent_object_id = C.object_id
WHERE OBJECT_NAME(DC.parent_object_id) = 'myTable'
AND COL_NAME(DC.parent_object_id,DC.parent_column_id) = 'myColumn'
;
Should return something like this:
[Table Name] [Column Name] [Constraint Name] [Constraint Type] [Default Value]
-------------------------------------------------------------------------------------------
myTable myColumn DF_myTable_myColumn DEFAULT_CONSTRAINT ('0')
If the [Default Value] returned is indeed (1), then it means that you have set the constraint properly and something else is at play here. It might be a trigger, or some other automated DML that you've forgotten/didn't know about, or something else entirely.
I am not the world's biggest fan of using a TRIGGER, but in a case like this, it could be handy. I find that one of the best uses for a TRIGGER is debugging little stuff like this - because it lets you see what values are being passed into a table without having to scroll through mountains of profiler data. You could try something like this (again, switching out the myTable and myColumn values with your actual table and column names):
CREATE TABLE Default_Check
(
Action_Time DATETIME NOT NULL DEFAULT GETDATE()
,Inserted_Value INT
);
CREATE TRIGGER Checking_Default ON myTable
AFTER INSERT, UPDATE
AS
BEGIN
INSERT INTO Default_Check (Inserted_Value)
SELECT I.myColumn
FROM Inserted I
;
END
;
This trigger would simply list the date/time of an update/insert done against your table, as well as the inserted value. After creating this, you could run a single INSERT statement, then check:
SELECT * FROM Default_Check;
If you see one row, only one action (insert/update) was done against the table. If you see two, something you don't expect is happening - you can check to see what. You will also see here when the 0 was inserted/updated.
When you're done, just make sure you DROP the trigger:
DROP TRIGGER Checking_Default;
You'll want to DROP the table, too, once it's become irrelevant:
DROP TABLE Default_Check;
If all of this still didn't help you, let me know.
In VB use
Property VariableName As Integer? = Nothing
And
In C# use
int? value = 0;
if (value == 0)
{
value = null;
}
Please check My Example:
create table emp ( ids int null, [DOJ] datetime NOT null)
ALTER TABLE [dbo].[Emp] ADD CONSTRAINT DF_Emp_DOJ DEFAULT (GETDATE()) FOR [DOJ]
1--Not working for Default Values
insert into emp
select '1',''
2 ---working for Default Values
insert into emp(ids) Values(13)
select * From emp
I'm new to PL/SQL. I'm using oracle 11g XE along with sql developer. I'm trying to create to create an after insert trigger as follows
create or replace trigger tr1
after
insert ON
employee
for each row
begin
print :new.emp_id;
end;
The employee table is as follows
create table employee
( emp_id varchar2(5) primary key,
emp_name varchar2(10),
salary number,
company varchar2(10) foreign key references companies(comp_name)
);
When I run the statement I got a 'enter binds' window for the bind variable :new. But I was confused that why do I need to enter the value for :new since it is pseudorecord. Then I entered 'employee' as the values for :new. Now I'm getting the following error.
Error(2,8): PLS-00103: Encountered the symbol "" when expecting one of the following: := . ( # % ; The symbol ":=" was substituted for "" to continue.
Your problem is not in the :new pseudorecord. The error is coming from the usage of print, which is used to print the bind variable used in successful PL/SQL block or used in an EXECUTE command. For example, you can use it this way:
VARIABLE n NUMBER
BEGIN
:n := 1;
END;
/
Then
PRINT n;
But if you want to test the value being inserted, you can use DBMS_OUTPUT.PUT_LINE like this:
create or replace trigger tr1
after
insert ON
employee
for each row
BEGIN
dbms_output.put_line(:new.emp_id);
END;
/
Enable DBMS_OUTPUT window in your SQL Developer, then run
insert into employee values(1, 'empName', 1000, 'ABC');
You'll see 1 printed out.
However, you can always test the value from the table. Because the value should be already inserted into table. You can just query.
I have a table named CUSTOMER, with few columns. One of them is Customer_ID.
Initially Customer_ID column WILL NOT accept NULL values.
I've made some changes from code level, so that Customer_ID column will accept NULL values by default.
Now my requirement is that, I need to again make this column to accept NULL values.
For this I've added executing the below query:
ALTER TABLE Customer MODIFY Customer_ID nvarchar2(20) NULL
I'm getting the following error:
ORA-01451 error, the column already allows null entries so
therefore cannot be modified
This is because already I've made the Customer_ID column to accept NULL values.
Is there a way to check if the column will accept NULL values before executing the above query...??
You can use the column NULLABLE in USER_TAB_COLUMNS. This tells you whether the column allows nulls using a binary Y/N flag.
If you wanted to put this in a script you could do something like:
declare
l_null user_tab_columns.nullable%type;
begin
select nullable into l_null
from user_tab_columns
where table_name = 'CUSTOMER'
and column_name = 'CUSTOMER_ID';
if l_null = 'N' then
execute immediate 'ALTER TABLE Customer
MODIFY (Customer_ID nvarchar2(20) NULL)';
end if;
end;
It's best not to use dynamic SQL in order to alter tables. Do it manually and be sure to double check everything first.
Or you can just ignore the error:
declare
already_null exception;
pragma exception_init (already_null , -01451);
begin
execute immediate 'alter table <TABLE> modify(<COLUMN> null)';
exception when already_null then null;
end;
/
You might encounter this error when you have previously provided a DEFAULT ON NULL value for the NOT NULL column.
If this is the case, to make the column nullable, you must also reset its default value to NULL when you modify its nullability constraint.
eg:
DEFINE table_name = your_table_name_here
DEFINE column_name = your_column_name_here;
ALTER TABLE &table_name
MODIFY (
&column_name
DEFAULT NULL
NULL
);
I did something like this, it worked fine.
Try to execute query, if any error occurs, catch SQLException.
try {
stmt.execute("ALTER TABLE Customer MODIFY Customer_ID nvarchar2(20) NULL");
} catch (SQLException sqe) {
Logger("Column to be modified to NULL is already NULL : " + sqe);
}
Is this correct way of doing?
To modify the constraints of an existing table
for example... add not null constraint to a column.
Then follow the given steps:
1) Select the table in which you want to modify changes.
2) Click on Actions.. ---> select column ----> add.
3) Now give the column name, datatype, size, etc. and click ok.
4) You will see that the column is added to the table.
5) Now click on Edit button lying on the left side of Actions button.
6) Then you will get various table modifying options.
7) Select the column from the list.
8) Select the particular column in which you want to give not null.
9) Select Cannot be null from column properties.
10) That's it.
this is my CASE/WHEN statement. But as you may see I get this error. I don't know why.
All I want to do is detect when something in field MAJKA is changed. So if some other fields of column MAJKA are empty don't touch them, but change the value to new value of those fields of column MAJKA which are NOT empty.
SQL Error: near "UPDATE": syntax error <CREATE TRIGGER [test]
AFTER UPDATE OF [MAJKA]
ON [unos_golub]
FOR EACH ROW
BEGIN
SELECT majka,
CASE WHEN majka=''
THEN
(UPDATE unos_golub SET broj_goluba=NEW.majka WHERE broj_goluba=OLD.majka)
ELSE
(UPDATE unos_golub SET broj_goluba=NEW.majka WHERE broj_goluba=OLD.majka
UPDATE unos_golub SET majka=NEW.majka WHERE majka=OLD.majka)
END
FROM unos_golub;
SQLite has no general mechanism to execute commands conditionally.
However, in triggers, you can use a WHEN condition on the entire trigger:
CREATE TRIGGER test_for_broj_goluba
AFTER UPDATE OF majka ON unos_golub
BEGIN
UPDATE unos_golub SET broj_goluba=NEW.majka WHERE broj_goluba=OLD.majka;
END;
CREATE TRIGGER test_for_majka
AFTER UPDATE OF majka ON unos_golub
WHEN NEW.majka <> ''
BEGIN
UPDATE unos_golub SET majka=NEW.majka WHERE majka=OLD.majka;
END;
(The first UPDATE is the same in both cases and thus does not need a WHEN.)
You're putting data manipulation (DML) statements where you need an expression that returns a value. Consider:
SELECT majka,
CASE WHEN majka=''
THEN
'it is empty'
ELSE
'it is not empty'
END
This will give you a column where the value is either 'it is empty' or 'it is not empty', depending on the value in the previous column.
You can't put a DML statement in that spot in the SQL -- the DML statement is not an expression with a value.