I am working on SQLite. I want to create a table namely user_role with two column role_id and role_name. And there is an another table namely default that contain role_name and default_val.
I want to set Default value of role_id in the time of creating the table user_role and the Default value have to be retrieved from the table default.
I am new to SQLite and have to idea about the way to doing such recursive query. Please help.
The documentation says:
An explicit DEFAULT clause may specify that the default value is NULL, a string constant, a blob constant, a signed-number, or any constant expression enclosed in parentheses.
You would need to use a subquery, which is not allowed.
However, you could use a trigger that sets the ID if none was specified:
CREATE TRIGGER user_role_id_default
AFTER INSERT ON user_role
FOR EACH ROW
WHEN NEW.role_id IS NULL
BEGIN
UPDATE user_role
SET role_id = (SELECT default_val
FROM "default"
WHERE role_name = NEW.role_name)
WHERE rowid = NEW.rowid;
END;
Related
I have an SQLite3 database that I would like to create. I want an INTEGER field (named "Length") to have a DEFAULT value that equals the length of the string in another field (named "Pattern").
CREATE TABLE knowledge (
Entry INTEGER PRIMARY KEY AUTOINCREMENT,
Priority TINYINT UNSIGNED CHECK (0 <= Priority < 15),
Pattern TEXT NOT NULL,
Length INTEGER UNSIGNED DEFAULT 'LENGTH(Pattern);'
);
However, the current table set-up does not "dynamically" set the value of "Length" as desired.
How can I properly set the DEFAULT value of "Length" to be the string length of the "Pattern" field?
The Default value you want to assign is dynamic which sqlite does not support. One solution is what CL. said. I would define the default value as 0 and use not one but two triggers (one for insert and another for update).
CREATE TRIGGER default_length_on_insert AFTER INSERT ON knowledge WHEN NEW.Length IS 0
BEGIN
UPDATE knowledge SET Length=length(NEW.Pattern) WHERE ROWID = NEW.ROWID;
END;
and
CREATE TRIGGER default_length_on_update AFTER UPDATE ON knowledge
BEGIN
UPDATE knowledge SET Length=length(NEW.Pattern) WHERE ROWID = NEW.ROWID;
END;
A default value must be a constant.
You coud use a trigger instead:
CREATE TRIGGER knowledge_length_default
AFTER INSERT ON knowledge
FOR EACH ROW
WHEN NEW.Length IS NULL
BEGIN
UPDATE knowledge
SET Length = length(NEW.Pattern)
WHERE Entry = NEW.Entry;
END;
Consider a simple self-referencing table in SQLite with the following fields
Create Table Test{
Id INTEGER PRIMARY KEY, <-- Alias for the RowId
Name TEXT NOT NULL CHECK(length(Name) > 0),
ParentId INTEGER REFERENCES Test(Id),
};
CREATE UNIQUE INDEX IX_UniqueNamePerLevel ON Test(ParentId, Name);
We're trying to set a uniqueness constraint on Name for all items which share the same ParentId. In other words, you can have two items with the name 'Joe' provided those items do not have the same ParentId.
The problem is that SQLite seems to treat nulls as distinct, meaning for any level except root items, the constraint works, but you can have fifteen 'Joe' entries all with a ParentId of 'null.'
Bonus points if you can show how to make that constraint trim leading and trailing whitespace on insert/update, and ignore case for the uniqueness constraint too.
SQLite treats NULLs in UNIQUE constraints as distinct for compatibility with other databases.
It is not possible to use a CHECK constraint for this because it would have to access other rows from the table, but subqueries are not allowed in CHECK.
You would have to use a trigger:
CREATE TRIGGER Test_ParentName_unique_insert_check
AFTER INSERT ON Test
FOR EACH ROW
WHEN NEW.ParentId IS NULL
BEGIN
SELECT RAISE(ABORT, 'root items must be unique, too')
FROM Test
WHERE ParentId IS NULL
AND Name = NEW.Name
AND Id <> NEW.Id;
END;
I am using asp.net2008 and MY SQL.
I want to auto-generate the value for the field username with the format as
"SISI001", "SISI002",
etc. in SQL whenever the new record is going to inserted.
How can i do it?
What can be the SQL query ?
Thanks.
Add a column with auto increment integer data type
Then get the maximum value of that column in the table using "Max()" function and assign the value to a integer variable (let the variable be 'x').
After that
string userid = "SISI";
x=x+1;
string count = new string('0',6-x.ToString().length);
userid=userid+count+x.ToString();
Use userid as your username
Hope It Helps. Good Luck.
PLAN A>
You need to keep a table (keys) that contains the last numeric ID generated for various entities. This case the entity is "user". So the table will contain two cols viz. entity varchar(100) and lastid int.
You can then have a function written that will receive the entity name and return the incremented ID. Use this ID concatenated with the string component "SISI" to be passed to MySQL for insertion to the database.
Following is the MySQL Table tblkeys:
CREATE TABLE `tblkeys` (
`entity` varchar(100) NOT NULL,
`lastid` int(11) NOT NULL,
PRIMARY KEY (`entity`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
The MySQL Function:
DELIMITER $$
CREATE FUNCTION `getkey`( ps_entity VARCHAR(100)) RETURNS INT(11)
BEGIN
DECLARE ll_lastid INT;
UPDATE tblkeys SET lastid = lastid+1 WHERE tblkeys.entity = ps_entity;
SELECT tblkeys.lastid INTO ll_lastid FROM tblkeys WHERE tblkeys.entity = ps_entity;
RETURN ll_lastid;
END$$
DELIMITER ;
The sample function call:
SELECT getkey('user')
Sample Insert command:
insert into users(username, password) values ('SISI'+getkey('user'), '$password')
Plan B>
This way the ID will be a bit larger but will not require any extra table. Use the following SQL to get a new unique ID:
SELECT ROUND(NOW() + 0)
You can pass it as part of the insert command and concatenate it with the string component of "SISI".
I am not an asp.net developer but i can help you
You can do something like this...
create a sequence in your mysql database as-
CREATE SEQUENCE "Database_name"."SEQUENCE1" MINVALUE 1 MAXVALUE 9999999999999999999999999999 INCREMENT BY 001 START WITH 21 CACHE 20 NOORDER NOCYCLE ;
and then while inserting use this query-----
insert into testing (userName) values(concat('SISI', sequence1.nextval))
may it help you in your doubt...
Try this:
CREATE TABLE Users (
IDs int NOT NULL IDENTITY (1, 1),
USERNAME AS 'SISI' + RIGHT('000000000' + CAST(IDs as varchar(10)), 4), --//getting uniqueness of IDs field
Address varchar(150)
)
(not tested)
I'm recently change my data table, I remove column and add a new column that define as identity = True and identity seed = 1, identity increment = 1.
When i tried to insert data to this table by STORE PROCEDURE i get this exception:
An explicit value for the identity column in table 'AirConditioner' can only be specified when a column list is used and IDENTITY_INSERT is ON.
I saw that i need to add this lines:
SET IDENTITY_INSERT [dbo].[AirConditioner] ON and finally OFF
I added and its still throw an exception...
My store procedure is attached as a picture
SQL Server will take care of assigning a value to your identity column. You should remove #ID from the insert statement and remove the IDENTITY_INSERT statements.
can only be specified when a column
list is used and IDENTITY_INSERT is
ON.
You're forgetting the first condition: the column list. The column list is a (usually) optional element between the table name and values. You should specify it like:
INSERT INTO AirConditioner (ID, CategoricNumber, ...)
VALUES(#ID, #CategoricNumber, ...)
Do NOT use set identity insert on. If you have an identity, you should be letting SQL server decide what value to put in there.
ALTER PROCEDURE [dbo].[AddAirConditioner] #CategoricNumber int, #Name nvarchar(50),
#PicName nvarchar(100), #ShortDetails nvarchar(200), #Details nvarchar(2000),
#Price int, #ImagePath nvarchar(500), #AirConditionerType nvarchar(50), #COP float,
#BTU float, #ProdType nvarchar(20), #ProdIndex int
AS
INSERT INTO AirConditioner VALUES( #CategoricNumber, #Name, #PicName,
#ShortDetails, #Details, #Price, #ImagePath, #AirConditionerType, #COP,
#BTU, #ProdType, #ProdIndex)
If you need to get the ID back for using in child tables, then use scope_identity or the output clause. Look these up in Books online to see how to use.
Try placing
SET IDENTITY_INSERT [dbo].[AirConditioner] ON
GO
Before the alter procedure
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.