I have a table (try), having a primary key (pk), several data fields (dx, dy, dz), and a time field (td). In sqlite3, I would like to:
Insert a record(pk, dx, dy, dz) if it (pk) does not exist.
If record exists, update it.
During update, If there is any change to some of the fields (dx,dy) update td to current time.
During update, If there was no change in above fields (dx,dy) leave td as is (original time).
REPLACE comes close to what I need, but it does an "insert" or "replace all", while I need an "insert" or "update a few".
Here is something that works, but this needs that 2 statements
One to check if record exists first, then next to do insert or update. How to perform these in a single statement?
-- Example table
CREATE TABLE try(
pk INTEGER PRIMARY KEY,
dx TEXT NOT NULL, -- update td if this changes.
dy TEXT, -- update td if this changes.
dz TEXT, -- no need to change td, if this changes.
td DATETIME DEFAULT (strftime('%s','now'))
);
-- 1. Check if record exists or not.
SELECT pk from try where pk=1;
-- 2.a If record does not exist, do this insert.
INSERT INTO try(pk, dx, dy, td) VALUES(1, 'data_x', 'data_y', 'data_z', strftime('%s', 'now'));
-- 2.b If record exists, update but be selective with td.
UPDATE try SET dx='data_x',
dy='data_y_new',
dz='data_z_new',
td=(CASE WHEN (try.dx IS NOT 'data_x' OR try.dy IS NOT 'data_y_new') THEN strftime('%s','now')
ELSE try.td
END)
WHERE pk=1;
I was able to combine the statements for my requirement, and here it goes just for reference, for someone else who might need it later. However, note that working with multiple statements within a transaction (as suggested by CL) might be simpler, in general..
REPLACE INTO try VALUES(1,
'data_x',
'data_y_new',
'data_z_new',
CASE WHEN EXISTS(SELECT td FROM try AS try2 WHERE (try2.pk IS 1 AND try2.dx IS 'data_x' AND try2.dy IS 'data_y_new'))
THEN (SELECT td FROM try AS try3 WHERE (try3.pk IS 1))
ELSE strftime('%s','now')
END);
Related
How is it possible to divide 2 columns and update with the result a third one?
UPDATE Table
SET success = (number_won_games / number_all_games)*100
WHERE name_game = 'some name'
This code is not updating my column, so I thought somebody of you guys could help me?
I believe your issue may be that number_won_games and number_all_games are integers and thus that the division will always be be 0 and thus 0 multiplied by 100 will then be 0, perhaps giving the impression that nothing is updated.
You could try casting number_won_games and number_all_games to REAL e.g. using :-
UPDATE Table
SET success = (CAST(number_won_games AS REAL) / CAST(number_all_games AS REAL)) * 100
WHERE name_game = 'some name';
Explanatory Example
Considering the following :-
DROP TABLE IF EXISTS t;
CREATE TABLE IF NOT EXISTS t (name_game TEXT, number_won_games INTEGER, number_all_games INTEGER, success REAL);
INSERT INTO t VALUES
('game1',10,20,0.12345678);
UPDATE t SET success = (number_won_games / number_all_games) * 100;
SELECT * FROM t;
UPDATE t SET success = (CAST(number_won_games AS REAL) / CAST(number_all_games AS REAL)) * 100;
SELECT * FROM t;
WHERE clause not needed, so has not been included.
Which inserts a row with 20 games played with 10 won (thus 50 as the success rate) and with success set to a non-zero value (to show that the first update does update) then
The first UPDATE as per your example result in :-
Whilst the second UPDATE, which casts the values to REAL results in :-
I feel like a trigger is your best bet here. I don't have access to a database at the moment, but something like this would probably work.
CREATE TABLE counter(id INTEGER PRIMARY KEY AUTOINCREMENT, success REAL, number_won_games REAL, number_all_games REAL);
CREATE TRIGGER counter_update_success AFTER UPDATE ON counter
BEGIN
UPDATE counter set NEW.success=((NEW.number_won_games/NEW.number_all_games)*100.0);
END;
CREATE TRIGGER counter_create_success AFTER INSERT ON counter
BEGIN
UPDATE counter set NEW.success=((NEW.number_won_games/NEW.number_all_games)*100.0);
END;
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
This is my table where i want my PNRNo to be generated as 'PNRRES001' for the first entry, and consecutive entries with 'PNRRES002','PNRRES002' so on.
So while creating table only i called that column to function which will generate the PNR no, User just has to enter the CustomerNo from the front end, and data wit PNR & Customer No will updated to the PNRDetails table.
CREATE TABLE PNRDetails(PNRNo AS (DBO.FuncIncPNR()) ,customerNo INT
--FUNCTION TO GENERATE THE PNR NUMBER
ALTER FUNCTION dbo.FuncIncPNR()
RETURNS VARCHAR(20)
AS
BEGIN
DECLARE #RR VARCHAR(20) SET #RR='PNRRESA001'
--here i have checked if no value is there then return the first value as 'PNRRESA001'
IF((SELECT COUNT(*)FROM PNRDetails)=0)
BEGIN
RETURN #RR
END
ELSE
-- if any value is there then take the last value and add 1 to it and update to the table
BEGIN
DECLARE #pnr VARCHAR(20),#S1 VARCHAR(20),#S2 INT
DECLARE PNRCursor CURSOR Static
FOR SELECT PNRNo FROM PNRDetails
OPEN PNRCursor
FETCH LAST FROM PNRNo INTO #pnr
SET #S1=SUBSTRING(#pnr,1,7)
SET #S2=RIGHT(#PNR,3)
SET #S2=#S2+1;
SET #pnr=#S1+#S2;
END
RETURN #pnr
END
--Here am inserting only customerNo as 5 and the PNR should be generated by my function
INSERT INTO PNRDetails VALUES(5)
--it shows 1 row updated :)
SELECT * FROM PNRDetails
-- but when i run select command it shows
--Maximum stored procedure, function, trigger, or view nesting level exceeded (limit 32). :(
U can run this.And pls do help if u find anything that could help me. any help will be appreciated...
Waiting for your kind response...
You could try to use a computed column and an identity column instead.
create table PNRDetails
(
ID int identity,
PNRNo as 'PNRRES'+right(1000+ID, 3),
customerNo int
)
I would suggest just using an IDENTITY instead as your id, let SQL Server handle the assignment of each id number with all it's built-in guards for concurrency, and leave the formatting up to the UI....or, create a computed column that defines the formatted version of the ID if you really do need it in the DB.
The risk you run with your intended approach is:
poor performance
concurrency issues - if loats of ids are being generate around the same time
If you are happy to change the table structure. Following will do the job.
CREATE TABLE [dbo].[PNRDetails](
[autoId] [int] IDENTITY(1,1) NOT NULL,
[prnNo] AS ('PNRRES'+right('000'+CONVERT([varchar](3),[dbo].[GetRowCount]([autoId]),(0)),(3))),
[customerNo] [int] NOT NULL,
CONSTRAINT [PK_Table1] PRIMARY KEY CLUSTERED
(
[autoId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
EDIT: to address identity issue for your requirement pls create following function and pass the [autoId] in as above (edited) in the computed column.
CREATE FUNCTION dbo.GetRowCount
(
#autoId INT
)
RETURNS INT
AS
BEGIN
DECLARE #RESULTS AS INT
SELECT #RESULTS = COUNT(autoId) FROM PNRDetails WHERE PNRDetails.autoId<#autoId
RETURN #RESULTS + 1
END
GO
--INSERT
INSERT INTO PNRDetails (customerNo) VALUES(5)
1) You can use an identity column in your database (INTEGER)
PROS: easy/No gaps in between generated ids
CONS: You have to select the inserted id & return via procedure/query
if you were to show it to end user
2) Define a database sequence
PROS: easy to implement/Can be stored/shown to user before the form is
even saved
CONS: Gaps in between if the certain id is once generated & not used
3). Select max(id) from column + 1
PROS: Useful where only single user inserts in a table
CONS: disastrous if you were in an environment where multiple users
were inserting in the same tablle (mismatched max ids)
4) Use a database trigger to autoincrement the column
PROS:automated
CONS: hard to debug (you have to make sure it don't breaks for some
reason otherwise insert fails)
Change the way your trigger works. Something like this
CREATE FUNCTION dbo.fn_FuncIncPNR(#ID int)
RETURNS varchar(20)
BEGIN
Declare #Retval varchar(20),
#No varchar(4)
Select #No = convert(varchar(4), #ID)
while Len(#No) < 4
Select #No = '0' + #No
Select #Retval = 'PNRRESA' + #No
RETURN #Retval
END
You will notice there is a parameter field
Change your table create to this
CREATE TABLE PNRDetails(PNRNo AS (dbo.fn_ShowPNRNo(wID)), wID int IDENTITY(1,1) NOT NULL, customerNo INT)
That should solve your problem
I've found a few "would be" solutions for the classic "How do I insert a new record or update one if it already exists" but I cannot get any of them to work in SQLite.
I have a table defined as follows:
CREATE TABLE Book
ID INTEGER PRIMARY KEY AUTOINCREMENT,
Name VARCHAR(60) UNIQUE,
TypeID INTEGER,
Level INTEGER,
Seen INTEGER
What I want to do is add a record with a unique Name. If the Name already exists, I want to modify the fields.
Can somebody tell me how to do this please?
Have a look at http://sqlite.org/lang_conflict.html.
You want something like:
insert or replace into Book (ID, Name, TypeID, Level, Seen) values
((select ID from Book where Name = "SearchName"), "SearchName", ...);
Note that any field not in the insert list will be set to NULL if the row already exists in the table. This is why there's a subselect for the ID column: In the replacement case the statement would set it to NULL and then a fresh ID would be allocated.
This approach can also be used if you want to leave particular field values alone if the row in the replacement case but set the field to NULL in the insert case.
For example, assuming you want to leave Seen alone:
insert or replace into Book (ID, Name, TypeID, Level, Seen) values (
(select ID from Book where Name = "SearchName"),
"SearchName",
5,
6,
(select Seen from Book where Name = "SearchName"));
You should use the INSERT OR IGNORE command followed by an UPDATE command:
In the following example name is a primary key:
INSERT OR IGNORE INTO my_table (name, age) VALUES ('Karen', 34)
UPDATE my_table SET age = 34 WHERE name='Karen'
The first command will insert the record. If the record exists, it will ignore the error caused by the conflict with an existing primary key.
The second command will update the record (which now definitely exists)
You need to set a constraint on the table to trigger a "conflict" which you then resolve by doing a replace:
CREATE TABLE data (id INTEGER PRIMARY KEY, event_id INTEGER, track_id INTEGER, value REAL);
CREATE UNIQUE INDEX data_idx ON data(event_id, track_id);
Then you can issue:
INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 2, 2, 3);
INSERT OR REPLACE INTO data VALUES (NULL, 1, 2, 5);
The "SELECT * FROM data" will give you:
2|2|2|3.0
3|1|2|5.0
Note that the data.id is "3" and not "1" because REPLACE does a DELETE and INSERT, not an UPDATE. This also means that you must ensure that you define all necessary columns or you will get unexpected NULL values.
INSERT OR REPLACE will replace the other fields to default value.
sqlite> CREATE TABLE Book (
ID INTEGER PRIMARY KEY AUTOINCREMENT,
Name TEXT,
TypeID INTEGER,
Level INTEGER,
Seen INTEGER
);
sqlite> INSERT INTO Book VALUES (1001, 'C++', 10, 10, 0);
sqlite> SELECT * FROM Book;
1001|C++|10|10|0
sqlite> INSERT OR REPLACE INTO Book(ID, Name) VALUES(1001, 'SQLite');
sqlite> SELECT * FROM Book;
1001|SQLite|||
If you want to preserve the other field
Method 1
sqlite> SELECT * FROM Book;
1001|C++|10|10|0
sqlite> INSERT OR IGNORE INTO Book(ID) VALUES(1001);
sqlite> UPDATE Book SET Name='SQLite' WHERE ID=1001;
sqlite> SELECT * FROM Book;
1001|SQLite|10|10|0
Method 2
Using UPSERT (syntax was added to SQLite with version 3.24.0 (2018-06-04))
INSERT INTO Book (ID, Name)
VALUES (1001, 'SQLite')
ON CONFLICT (ID) DO
UPDATE SET Name=excluded.Name;
The excluded. prefix equal to the value in VALUES ('SQLite').
Firstly update it. If affected row count = 0 then insert it. Its the easiest and suitable for all RDBMS.
Upsert is what you want. UPSERT syntax was added to SQLite with version 3.24.0 (2018-06-04).
CREATE TABLE phonebook2(
name TEXT PRIMARY KEY,
phonenumber TEXT,
validDate DATE
);
INSERT INTO phonebook2(name,phonenumber,validDate)
VALUES('Alice','704-555-1212','2018-05-08')
ON CONFLICT(name) DO UPDATE SET
phonenumber=excluded.phonenumber,
validDate=excluded.validDate
WHERE excluded.validDate>phonebook2.validDate;
Be warned that at this point the actual word "UPSERT" is not part of the upsert syntax.
The correct syntax is
INSERT INTO ... ON CONFLICT(...) DO UPDATE SET...
and if you are doing INSERT INTO SELECT ... your select needs at least WHERE true to solve parser ambiguity about the token ON with the join syntax.
Be warned that INSERT OR REPLACE... will delete the record before inserting a new one if it has to replace, which could be bad if you have foreign key cascades or other delete triggers.
If you have no primary key, You can insert if not exist, then do an update. The table must contain at least one entry before using this.
INSERT INTO Test
(id, name)
SELECT
101 as id,
'Bob' as name
FROM Test
WHERE NOT EXISTS(SELECT * FROM Test WHERE id = 101 and name = 'Bob') LIMIT 1;
Update Test SET id='101' WHERE name='Bob';
I believe you want UPSERT.
"INSERT OR REPLACE" without the additional trickery in that answer will reset any fields you don't specify to NULL or other default value. (This behavior of INSERT OR REPLACE is unlike UPDATE; it's exactly like INSERT, because it actually is INSERT; however if what you wanted is UPDATE-if-exists you probably want the UPDATE semantics and will be unpleasantly surprised by the actual result.)
The trickery from the suggested UPSERT implementation is basically to use INSERT OR REPLACE, but specify all fields, using embedded SELECT clauses to retrieve the current value for fields you don't want to change.
I think it's worth pointing out that there can be some unexpected behaviour here if you don't thoroughly understand how PRIMARY KEY and UNIQUE interact.
As an example, if you want to insert a record only if the NAME field isn't currently taken, and if it is, you want a constraint exception to fire to tell you, then INSERT OR REPLACE will not throw and exception and instead will resolve the UNIQUE constraint itself by replacing the conflicting record (the existing record with the same NAME). Gaspard's demonstrates this really well in his answer above.
If you want a constraint exception to fire, you have to use an INSERT statement, and rely on a separate UPDATE command to update the record once you know the name isn't taken.
I've just thought about best way to store comments in database with appropriate numbers according to the article.
The idea is to store comments with composite primary key (commentId, articleId) where commentId is generated according to the given articleId. The system of generating should has same principle as IDENTITY generated columns in SQL Server, because if someone delete the comment, the number will be never used again. I guess there is not any functionality in Microsoft SQL Server to do that with composite PK, so I am asking about some replacement for this solution.
First thought was to use transaction to get MAX(commentId) + 1, but I am looking for something more abstract (maybe INSTEAD OF trigger), something that could be used for example in LINQ with no knowledge of the background, just insert to the appropriate table all required values (so no commentId) and save it.
I would use an autogenerated identity column for the commentId and have it be the primary key alone. I'd create an index on the articleId for look ups. I would also have createdDate column that is autopopulated with the current date on insertion -- mark it as db generated and readonly in LINQ so it doesn't require or try to insert/update the value. To get a numbering -- if showing them by date isn't enough -- I'd order by createdDate inversed and assign a numeric value in the select using Row_Number() or a numbering on the client side.
I would use an identity column as the key for the comments, why do you need a numbering for the comments stored in the database?
Thank you for responses, I wanted something with numbered comments because of referencing in the text of comments. I did not want to make reaction by names, sometimes one person reacts more times, so with this system, I will know to which one the person is replying.
So today I made up this INSTEAD OF INSERT trigger:
CREATE TRIGGER InsertComments ON Comments
INSTEAD OF INSERT
AS
DECLARE #Inserted TABLE
(
ArticleId INT NOT NULL,
UserId INT NOT NULL,
CommentDate DATETIME NOT NULL,
Content NVARCHAR(1000) NOT NULL,
RowNumber INT NOT NULL
)
INSERT INTO #Inserted
SELECT ArticleId, UserId, CommentDate, Content, ROW_NUMBER() OVER (ORDER BY CommentDate) AS RowNumber
FROM INSERTED
DECLARE #NumberOfRows INT = (SELECT COUNT(*) FROM #Inserted)
DECLARE #i INT = 1
WHILE (#i <= #NumberOfRows)
BEGIN
SET TRANSACTION ISOLATION LEVEL SERIALIZABLE
BEGIN TRAN
DECLARE #CommentId INT = (SELECT ISNULL(MAX(CommentId), 0)
FROM Comments WHERE ArticleId = (SELECT ArticleId
FROM #Inserted WHERE RowNumber = #i)) + 1
INSERT INTO Comments(CommentId, ArticleId, UserId, CommentDate, Content)
SELECT #CommentId, ArticleId, UserId, CommentDate, Content
FROM #Inserted WHERE RowNumber = #i
COMMIT
SET #i = #i + 1
END
I know this is not the perfect solution, but it works exactly how I needed. If any of you has some comments, I'll be happy to read them.