Im attempting to do a SELECT on data in a table that contains prefixes, and I have the "keyword".
So unlike a normal search where the prefix/keyword is contained in the row data, and that the prefix/keyword is shorter (or contained in) a possible row of data.
This is the opposite. If have prefixes in rows and I want to find the best matching row based on the (longer) word/phase.
CREATE TABLE table1 (id INT NOT NULL AUTO_INCREMENT, keyCode VARCHAR(45) NULL, Username VARCHAR(45) NULL, PRIMARY KEY (id));
INSERT INTO table1(keyCode,Username)VALUES('123','Peter')
INSERT INTO table1(keyCode,Username)VALUES('456','Paul')
INSERT INTO table1(keyCode,Username)VALUES('1234','John')
Now let's say the phrase I have been given is longer than the prefix in the data.
Like this:
SELECT * FROM table1 WHERE keyCode LIKE '123456%';
I know this will not work, but I would like to return the Row with User 'John'.
How?
(I can use stored procedures)
You may phrase your LIKE expression in the reverse order:
SELECT *
FROM table1
WHERE '123456' LIKE CONCAT(keyCode, '%');
This would compare, for example, '123456' against '1234%', which should be a match in this case.
You can check for the existence of the keyCode prefix at the beginning of your string using LOCATE(). For example:
SELECT *
FROM table1
WHERE LOCATE(keyCode,'123456') = 1;
Related
I've got a SQL 2008 R2 table defined like this:
CREATE TABLE [dbo].[Search_Name](
[Id] [bigint] IDENTITY(1,1) NOT NULL,
[Name] [nvarchar](300) NULL),
CONSTRAINT [PK_Search_Name] PRIMARY KEY CLUSTERED ([Id] ASC))
Performance querying the Name field using CONTAINS and FREETEXT works well.
However, I'm trying to keep the values of my Name column unique. Searching for an existing entry in the Name column is unbelievably slow for a large number of names (usually batches of 1,000), even with an index on the Name field. Query plans indicate I'm using the index as expected.
To search for an existing value, my query looks like this:
SELECT TOP 1 Id, Name from Search_Name where Name = 'My Name Value'
I've tried duplicating the Name column to another column and searching on the new column, but the net effect was the same.
At this point, I'm thinking I must be mis-using this feature.
Should I just stop trying to prevent duplication? I'm using a linking table to join these search name values to the underlying data. It seems somehow 'dirty' to just store a whole bunch of duplicate values...
...or is there faster way to take a list of 1,000 names and see which ones are already stored in the database?
The first change to make is to get the entire list to SQL Server at one time. Regardless of how you add the names to the existing table, doing it as a set operation will make a big difference in performance.
Passing the List as a table-valued parameter (TVP) is a clean way to handle it. Have a look here for an example. You can still use an OUTPUT clause to track which rows did or didn't make the cut, for example:
-- Some sample existing names.
declare #Search_Name as Table ( Id Int Identity, Name VarChar(32) );
insert into #Search_Name ( Name ) values ( 'Bob' ), ( 'Carol' ), ( 'Ted' ), ( 'Alice' );
select * from #Search_Name;
-- Some (prospective) new names.
declare #New_Names as Table ( Name VarChar(32) );
insert into #New_Names ( Name ) values ( 'Ralph' ), ( 'Alice' ), ( 'Ed' ), ( 'Trixie' );
select * from #New_Names;
-- Add the unique new names.
declare #Inserted as Table ( Id Int, Name VarChar(32) );
insert into #Search_Name
output inserted.Id, inserted.Name into #Inserted
select New.Name
from #New_Names as New left outer join
#Search_Name as Old on Old.Name = New.Name
where Old.Id is NULL;
-- Results.
select * from #Search_Name;
-- The names that were added and their id's.
select * from #Inserted;
-- The names that were not added.
select New.Name
from #New_Names as New left outer join
#Inserted as I on I.Name = New.Name
where I.Id is NULL;
Alternatively, you could use a MERGE statement and OUTPUT the names that were added, those that weren't, or both.
I'm trying to create a simple table where I insert field and I do some checks in MySql. I've used Microsoft SQL relatively easy. Instead, MySql give evrrytime query errors without even specifying what's going on. Poor MySql software design apart, here's what I'm trying to do:
1 table with 4 fields with an autoincremental autogenerated number to det an ID as primary key
CREATE TABLE `my_db`.`Patients_table` (
`ID_Patient` INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY ,
`Patient_name` VARCHAR( 200 ) NOT NULL ,
`Recovery_Date` DATETIME NOT NULL ,
`Recovery_count` INT NOT NULL
) ENGINE = MYISAM
a simple stored procedure to insert such fields and check if something exist before inserting:
CREATE PROCEDURE nameInsert(IN nome, IN data)
INSERT INTO Patients_table (Patient_name,Recovery_Date) values (nome,data)
IF (EXISTS (SELECT Recovery_count FROM Tabella_nomi) = 0) THEN
INSERT INTO (Patients_table (Recovery_count)
ELSE
SET Recovery_count = select Recovery_count+1 from Patients_table
END
this seems wrong on many levels and MySQL useless syntax checker does not help.
How can I do this? Thanks.
There seems to be a lot wrong with this block of code. (No offense intended!)
First, Procedures need to be wrapped with BEGIN and END:
CREATE PROCEDURE nameInsert(IN nome, IN data)
BEGIN
...[actually do stuff here]
END
Second, since your table is declared with all fields as NOT NULL, you must insert all fields with an INSERT statement (this includes the Recovery_Date column, and excludes the AUTO_INCREMENT column). You can add DEFAULT CURRENT_TIMESTAMP to the date column if you want it to be set automatically.
INSERT INTO Patients_table (Patient_name,Recovery_Date) values (nome,data)
Third, what exactly is your IF predicate doing?
EXISTS (SELECT Recovery_count FROM Tabella_nomi) = 0
If you want to check if a row exists, don't put the = 0 at the end. Also, Tabella_nomi isn't declared anywhere in that procedure. Also, your SELECT statement should have a WHERE clause, since I'm assuming you want to select a specific row (this is going to select a result set of all recovery_counts).
Fourth, the second INSERT statement seems a little messy. It should look more like the first INSERT, and keep the point I made above in mind.
INSERT INTO (Patients_table (Recovery_count)
Fifth, the ELSE statement
SET Recovery_count = select Recovery_count+1 from Patients_table
Has some problems too. SET is meant for setting variables, not values in rows. I'm not 100% sure what your intent is from this statement, but it looks like you meant to increment the Recovery_count column of a certain row if it already exists. In which case, you meant to do something like this:
UPDATE Patients_table SET Recovery_count = Recovery_count+1 WHERE <conditional predicate>
Where the conditional predicate is something like this:
Patients_name = nome
Try these things, and look at the errors it gives you when you try to execute the CREATE STATEMENT. I bet they're more useful then you think!
I have a simple table like this
CREATE TABLE authid(
id INT NOT NULL AUTO_INCREMENT,
authid VARCHAR(128) NOT NULL UNIQUE,
PRIMARY KEY(id)
);
Now if I insert a value with
INSERT INTO authid(authid) VALUES('test');
It will work fine and return the inserted id the first time, but if I do it again when the authid already exists (notice that we have authid marked as UNIQUE) it will return an error.
Is there a way achieve this this in one SQL statement: Insert it, get the id and if it already exists, still get the id.
Take a look at this: http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html
If you're using MySQL 5.0 or higher you can use the "INSERT ... ON DUPLICATE KEY UPDATE" syntax. You may be able to combine that with LAST_INSERT_ID() (I'm not positive about that)
So:
insert into authid (authid) values ('test') on duplicate key update id=LAST_INSERT_ID(id), authid='test';
select LAST_INSERT_ID();
Well indeed if you try to insert 2 times the same value in a UNIQUE field, it won't work, that's the point of UNIQUE fields.
If I understand well, you want to know if it's possible whether to use an INSERT or an UPDATE statement depending on the existance of an item or not ? Then you need 2 queries, 1 to test existence, the other to insert new value or update existing one
Insert the value conditionally (i.e. if it doesn't exist). Whether the insert takes place or not, by the end of the statement the result will be the same: the value will be in the table. So, just select the ID of the row that matches that value. Or, speaking in SQL, like this:
INSERT INTO authid (authid)
SELECT 'test'
WHERE NOT EXISTS (
SELECT *
FROM authid
WHERE authid = 'test'
);
SELECT id
FROM authid
WHERE authid = 'test'
;
This is a follow up to a previous issue I had posted here.
I created a test table:
CREATE TABLE `my_test_table` (
`record_id` INT(11) UNSIGNED NOT NULL AUTO_INCREMENT,
`col1` BINARY(20) NULL DEFAULT NULL,
`col2` CHAR(40) NULL DEFAULT NULL,
PRIMARY KEY (`record_id`)
)
Then ran the statement:
INSERT INTO my_test_table (col1, col2) VALUES(sha1('test'), sha1('test') );
The data looks like...
1 0x6139346138666535636362313962613631633463 a94a8fe5ccb19ba61c4c0873d391e987982fbbd3
I'm not sure how I can select against the VARBINARY column. I can select against the CHAR like:
SELECT * FROM my_test_table WHERE col2 = sha1('test');
I've tried
SELECT * FROM my_test_table WHERE col1 = hex(sha1('test'));
And other variations but can't seem to find a solution (if there is one). I need to be able to check to see if a value already exists in the database before I allow a new insert. I was looking at VARBINARY and BINARY based on previous suggestions. Thanks.
I have not read your previous question, but based on the source code in this question, you are only storing the first 20 characters of the sha1 hash in col1, so if you want to select it you should just look for the first 20 characters of the sha1 hash.
For example:
SELECT *
FROM my_test_table
WHERE col1 = left(sha1('test'),20);
Data truncation: Data too long for column 'col1' at row 1: INSERT INTO my_test_table (col1, col2) VALUES(sha1('test'), sha1('test') )
Can this be the reason why you cannot select the data properly?
BTW the sha1('test') returns a STRING of hex characters...
You should use unhex(sha1('test')) when inputing data as a hex string, or else it wont be entered as acsii values which wont work with matching at all
SELECT * FROM my_test_table WHERE col1 = unhex(sha1('test'));
should be the matching query also.
Using strictly SQL (no PHP or anything else), is it possible to create a table and insert default data into that table only if that table doesn't exist?
Use the CREATE TABLE ... SELECT format:
create table if not exists tablename as
select * from defaultdata;
Here is one way of doing it:
CREATE TABLE IF NOT EXISTS T (
ID int(10) unsigned NOT NULL primary key,
NAME varchar(255) NOT NULL
);
REPLACE INTO T SELECT 1, 'John Doe';
REPLACE INTO T SELECT 2, 'Jane Doe';
REPLACE is a MySQL extension to the SQL standard that either inserts, or deletes and inserts.
You might do a select on the one of the meta data tables
if(not exists select * from whatever_meta where table_name = "whatever)
begin
...
end
You would have to do some research to figure out how exactly...
Can you store the table status as a variable, then use that variable to determine whether to insert data? Ex:
#status = SHOW TABLES LIKE 'my_table';
INSERT INTO my_table VALUES (1,'hello'),(2,'world') WHERE #status <> false;
The problem with Paul Morgan's answer is that it expects data to already exist in another table. Jonas' answer would be extremely resource exhaustive, especially if there's a lot of REPLACES (which are unnecessary if the table exists).
May be I am missing the point but why can't the default data be a set of insert statements...and what one simply needs to do is create the table if it does not exist followed by insert statements...that ways the default data does not have to exist in a different table.