In Sql I check if a table exist with this code:
IF NOT EXISTS (SELECT NAME FROM SYSOBJECTS
WHERE NAME = 'Plane')
CREATE TABLE Plane(Flight int)
How to do this check if a table not exist then i create it in Oracle because it throws exception if i try to create already existing table?
you can check the data dictionary for that table
select table_name from user_tables where table_name='MYTABLE';
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
Related
I have a MVC-Project with a DB-First EDMX file from a production database.
Let's say table Person has an identity-column named ID.
I also have a copy of this database where I have turnd OFF the Identity-Option for the ID column. My goal is to synchronize data between these two databases.
To connect to each of these databases I use the same context-class with different connection-strings.
The problem with this is, that when I try to add a copy of a row from table Person from productionDB to my copyDB I get an error, because EntityFramework is trying to insert NULL for the ID column. I know that this is totally normal, because the EDMX-File has set identity to TRUE for the ID-column of table Person, but is there a way to programatically change this behaviour?
Context prod = new Context("ProductionConnectionString");
Context prodCopy = new Context("CopyConnectionString");
var prodEntity = prod.Person.First(); \\ RETURNS A PERSON WITH ID 1
prodCopy.Person.Add(prodEntity):
prodCopy.SaveChanges(); \\THIS WILL THROW AN EXCEPTION BECAUSE EF WILL REPLACE 1 WITH NULL BECAUSE IDENTITY OPTION
Any ideas?
My problem is with the generic "Delete" in the BidController I am getting the typical Error:
The DELETE statement conflicted with the REFERENCE constraint "fkw_....". The conflict occurred in database table ..., column ....
The statement has been terminated.
Thank you so much for any and all help.
Try updating the ActiveBidId with a null value and then delete the bids.That way you break the link between the Item and Bid and than you can remove the Data from Bids.
Try making the relationship as OPTIONAL. This way your items can have null Foreign Keys.
If you are using database first approach:
CREATE TABLE Item(
ItemId INT PRIMARY KEY,
ActiveBidId INT NULL FOREIGN KEY REFERENCES Bid(BidId)
// ...
);
If you already created the table, then you can alter your table as follows:
ALTER TABLE Item
DROP CONSTRAINT FK_ActiveBidConstraint -- The name of your constraint
GO
ALTER TABLE Item
ADD CONSTRAINT FK_ActiveBidConstraint FOREIGN KEY (ActiveBidId) -- The name of your constraint
REFERENCES Bid(BidId);
Apparently I am able to set the GUID to null, so I am posting a simple answer.
In my BidController I have updated my code:
item = null;
This removes the reference to the bid and so the bids are free to be removed!
in my SAPUI5-Application I got the following function that takes the data and creates an entry in my HANA DB:
onCreateNewCustomer: function(){
var oEntry = {};
oEntry.NAME = this.byId("name").getValue();
oEntry.CITY = this.byId("city").getValue();
oEntry.PHONE = this.byId("phone").getValue();
oEntry.ID = this.byId("id").getValue();
// Post data to the server
this.getOwnerComponent().getModel("CustomerModel").create("/Customer", oEntry, null);
this.byId("createCustomer").close();
//location.reload();
}
The creating process works and my entries get saved. In the next step I wanted to implement my table in HANA in that way, that the ID of the entries will be autoincremented so the user does not have to enter it. I used the following command to create my table:
create column table TABLE
(ID bigint not null primary key generated by default as IDENTITY,
FIRSTNAME nvarchar(30))
That worked, table is created. The problem now is, if I use the code above without providing the ID, the following error is logged by the console:
The following problem occurred: HTTP request failed 400,Bad Request,The serialized resource has an missing value for member 'ID'.
The entry does not get saved in my DB. If I execute the following SQL-Statements in my HANA Workbench without providing the ID, it works:
insert into TABLE (FIRSTNAME) values (‘David’);
insert into TABLE (FIRSTNAME) values (‘Mike’);
insert into TABLE (FIRSTNAME) values (‘Bobby’);
So I did some searching on google but did not find a proper solution on how to do this. My goal is that the entry gets saved and the ID is provided by my HANA DB without providing it from my SAPUI5 Application.
Probably you are using ODataV2 XSODATA implementation which does not support auto-increment. The possible solution here is to use a database sequence and then with a separate request get a value from it and use it in OData create statement.
Did you try creating a new record by commenting out the below code like ?
oEntry.ID = this.byId("id").getValue();
With identity fields, if you provide the value you have to explicitly identify that you are providing the column value. Otherwise, just omit the columnn name and value from the INSERT command.
I am not able to set foreign key using stephencelis SQLite.swift.
t.foreignKey(user_id, references:"user_mstr",user_id)
I have two tables user_master and user_details. How to set user_id as a foreign key in user_detail table. I am getting below error.
Cannot invoke foreignkey with an arguement list of type (Expression<string>),
You're passing string to references. It should be like
let user_id = Expression<String>("user_id")
let user_mstr = Table("user_mstr")
//cate t somehow
t.foreignKey(user_id, references: user_mstr, user_id)
I want a simple SQL (trigger) for duplicate checking.
My table name is test1 with 2 columns, code and sname. Before inserting a new record, check if the record already exists: if it does, generate an error and do not insert; if it does not, let the insert proceed.
How do I do that?
The simplest, most reliable way to ensure that there is no duplicate data in the table is not using triggers at all, but using UNIQUE or PRIMARY KEY constraints:
CREATE TABLE test1
(
code INTEGER NOT NULL PRIMARY KEY,
sname VARCHAR(32) NOT NULL UNIQUE
);
The four constraints (two NOT NULL, one PRIMARY KEY, one UNIQUE) automatically ensure that no duplicate records are inserted into the table.
If you choose to add a trigger, it will be duplicating the work that is done by these constraints.
As to how to do it, you will need to create a stored procedure which is invoked from the trigger statement. It will be given the new code and new name, and will do a SELECT to see whether any matching record occurs, and will raise an exception if it does and will not raise an exception if not.
CREATE PROCEDURE trig_insert_test1(ncode INTEGER, nname VARCHAR(32))
DEFINE ocode INTEGER;
FOREACH SELECT code INTO ocode
FROM test1
WHERE code = ncode OR sname = nname
RAISE EXCEPTION -271, -100, "Value to be inserted already exists in table test1";
END FOREACH;
END PROCEDURE
Then you use:
CREATE TRIGGER ins_test1 INSERT ON test1
REFERENCING NEW AS NEW
FOR EACH ROW (EXECUTE PROCEDURE ins_trig_test1(new.code, new.sname))
In Informix 4GL, you can either create strings containing these statements, and then PREPARE and EXECUTE (and FREE) them, or you can use SQL blocks:
SQL
CREATE TRIGGER ins_test1 INSERT ON test1
REFERENCING NEW AS NEW
FOR EACH ROW (EXECUTE PROCEDURE ins_trig_test1(new.code, new.sname))
END SQL
But, as I said at the outset, using triggers for this is not the best way to go; it is redundant given the table definition.
I've not run any of the SQL or SPL past the server; you'll need to check that the semi-colons are in the right places in the SPL, as SPL is fussy about that.
You can find the syntax for the SQL and SPL statements in the Informix 11.70 Information Centre.