I have a table
tbl_group
----------
groupId (pk)
groupName
and another table
tbl_group_head
--------------
groupHeadId (pk)
groupId (fk)
designation
I have already inserted data in tbl_group like 1002,cs and 1003,mca.
How to insert in tbl_group_head in joomla(2.5)?
Related
Is it possible to specify which is the primary key on creating table as select statement? My aim is to include the declaration of primary key on the create table not modifying the table after the creation.
CREATE TABLE suppliers
AS (SELECT company_id, address, city, state, zip
FROM companies
WHERE company_id < 5000);
Yes, it's possible. You would need to specify columns explicitly:
CREATE TABLE suppliers (
company_id primary key,
address,
city,
state,
zip
)
AS
SELECT company_id, address, city, state, zip
FROM companies
WHERE company_id < 5000;
Here is a demo
Note: in this case primary key constraint will be given a system-generated name. If you want it to have a custom name you'd have to execute alter table suppliers add constraint <<custom constraint name>> primary key(<<primary_key_column_name>>) after executing(without primary key specified) CREATE TABLE suppliers.. DDL statement.
Yes, it's possible.You can try referring below example.
create table student (rollno ,student_name,score , constraint pk_student primary key(rollno,student_name))
as
select empno,ename,sal
from emp;
You can create Suppliers table explicitly and if any column have primary key in companies table, then copy that structure from companies table.
Or
Create a same column defining primary key that you want and copy that column from companies table!
I want to create a table department:
COLUMN NAME DATATYPE SIZE CONSTRAINT
dept_id number 4 Primary key
prod_id number 4 Foreign key
I tried this:
CREATE TABLE Department(
dept_id number(4) primary key,
prod_id number(4) foreign key);
It shows error. How can I add a foreign key constraint to this table?
A foreign key defines a relationship between your table DEPARTMENT and another table with a primary key. It means, you cannot create a row in DEPARTMENT with a PROD_ID of 1234 unless there is a pre-existing row in the designated parent table with a value of 1234 as its primary key.
So do you have such an existing parent table? if so you need to include its name in the foreign key definition. Otherwise you must create it.
Let's say the parent table is PRODUCT:
create table product (
prod_id number(4) primary key
, name varchar2(32) not null
);
Then you can create DEPARTMENT with a foreign key like this:
CREATE TABLE Department(
dept_id number(4) primary key,
prod_id references PRODUCT );
Yep, that's all the syntax you need: it automatically creates a column PROD_ID with the same datatype and precision as the primary key column of the referenced table. More verbose syntax is available. Read the Oracle SQL documentation to find out more.
I assume that the other table is named other_table_name and that it contains a primary key named prod_id.
CREATE Department (
dept_id number(4) primary key,
prod_id number(4) REFERENCES other_table_name (prod_id)
);
or a different syntax
CREATE Department (
dept_id number(4) primary key,
prod_id number(4)
...
CONSTRAINT fk_prod_id
FOREIGN KEY (prod_id)
REFERENCES other_table_name (prod_id)
);
How to link the MgrId in ManagerProject to EmpId in the Employee table ?
This is wat I tried :
CREATE TABLE Employee(EmpId varchar2(5),
EmpName varchar2(25),
DeptId varchar2(3),
Salary Number(8),
Constraint PK_addn primary key (EmpId, DeptId),
Constraint fk_Department foreign key (DeptId) references Department (DeptId));
But the second table failed to be created :
CREATE TABLE ManagerProject(ProjId varchar2(4),
MgrId varchar2(5),
StartDate Date,
EndDate Date,
Constraint fk_managerproject foreign key (MgrId) references Employee (EmpId),
Constraint PK_Managerproject Primary key(ProjId, MgrId, StartDate));
It displays
ORA-02270: no matching unique or primary key for this column-list
The error message says that you are trying to create a FK referencing a column on which there is no Unique or Primary Key constraint.
Assuming that you don't want to add the column DeptId to ManagerProject, you need to add a unique key on employee:
alter table Employee add constraint empId_UK unique ( empId)
But this strongly depends on what your schema should be.
If you want to add the column DeptId to ManagerProject, you will need to edit your FK to both use EmpId and DeptId in referencing employee.
I would like to know:
How to rename a table column in Oracle 10g?
SQL> create table a(id number);
Table created.
SQL> alter table a rename column id to new_id;
Table altered.
SQL> desc a
Name Null? Type
----------------------------------------- -------- -----------
NEW_ID NUMBER
The syntax of the query is as follows:
Alter table <table name> rename column <column name> to <new column name>;
Example:
Alter table employee rename column eName to empName;
To rename a column name without space to a column name with space:
Alter table employee rename column empName to "Emp Name";
To rename a column with space to a column name without space:
Alter table employee rename column "emp name" to empName;
alter table table_name rename column oldColumn to newColumn;
suppose supply_master is a table, and
SQL>desc supply_master;
SQL>Name
SUPPLIER_NO
SUPPLIER_NAME
ADDRESS1
ADDRESS2
CITY
STATE
PINCODE
SQL>alter table Supply_master rename column ADDRESS1 TO ADDR;
Table altered
SQL> desc Supply_master;
Name
-----------------------
SUPPLIER_NO
SUPPLIER_NAME
ADDR ///////////this has been renamed........//////////////
ADDRESS2
CITY
STATE
PINCODE
alter table table_name
rename column old_column_name/field_name to new_column_name/field_name;
example: alter table student rename column name to username;
I have a 'users' and 'notifications' tables.
The tables definition are:
users notifications
------- -------------
ID (PK) ID (PK)
Name Name
users_ID (FK / Relation)
When I do:
MyUserEntity.notifications.clear();
MyContext.SaveChanges();
The users_ID column value(s) for the corresponding user entity are set to NULL, but I want the rows to be deleted.
What am I missing?
Thanks!
Try
foreach(var notification in MyUserEntity.notifications.ToList())
{
MyContext.DeleteObject(notification);
}
MyContext.SaveChanges();