Insert if doesn't exist fail if table empty [duplicate] - mysql

This question already has answers here:
How can I do 'insert if not exists' in MySQL?
(11 answers)
Closed 6 years ago.
I used the following command to avoid duplicates in a table :
INSERT INTO mytable (num,name)
SELECT 2,'example' FROM mytable WHERE NOT EXISTS
(SELECT * FROM mytable WHERE num=2 AND name='example') LIMIT 1;
It is working but NOT if mytable is empty.
mytable also contain a AUTO_INCREMENT id.
CREATE TABLE mytable (
id int(11) NOT NULL auto_increment,
num int(11) NOT NULL,
name varchar(100) NOT NULL,
PRIMARY KEY (id)
);
Do you recommanded another method or a workaround ?


In my case replacing mytable by DUAL did the trick. (But i have no idea why)
INSERT INTO mytable (num,name)
SELECT 2,'example' FROM mytable WHERE NOT EXISTS
(SELECT * FROM mytable WHERE num=2 AND name='example') LIMIT 1;
Replaced by :
INSERT INTO mytable (num,name)
SELECT 2,'example' FROM DUAL WHERE NOT EXISTS
(SELECT * FROM mytable WHERE num=2 AND name='example') LIMIT 1;
Thanks for the help.


You can create Unique column by using MySQL UNIQUE
Just update your CREATE TABLE query like below
CREATE TABLE mytable (
id int(11) NOT NULL auto_increment,
num int(11) NOT NULL,
name varchar(100) NOT NULL,
PRIMARY KEY (id),
UNIQUE (num) # You can define Unique column like this
);
Note: Then you no need to check Unique value when Save to Database.
And try to use normal SQL query for inserting Data
INSERT INTO mytable (num,name) VALUES(2,'example')


You can do something like
Select * from tbl where _____ = ______
Then add if statement if results are available then insert or otherwise leave


Why do not you simply use INSERT IGNORE. Also why do you want to copy the data from same table?

Related

LEFT JOIN table to find non matching rows, same table

I have a table that looks like this:
id int primary key
uniqueID string --not uniquely indexed
foreignKeyID int --foreignKey to another table
I want to find all the uniqueIds in this table that exist for foreign key 1 that do not exist for foreign key 2
I thought I could do something like this:
SELECT * FROM table t1
LEFT JOIN table t2
ON t1.uniqueID = t2.uniqueID
WHERE
t1.foreignKeyID = 1
AND t2.uniqueID IS NULL
However this is never giving me results. I can make it work with a NOT IN subquery but this is a very large table so I suspect a solution using joins will be faster.
Looking for the best way to structure this query.
Here's an sample data set and SQL Fiddle with an example of the working NOT IN query I am trying to convert to a LEFT JOIN:
CREATE TABLE `table` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`uniqueID` varchar(255),
`foreignKeyID` int(5) unsigned NOT NULL DEFAULT 0,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
INSERT INTO `table` (uniqueID, foreignKeyID) VALUES ('aaa', 1), ('bbb', 1);
http://sqlfiddle.com/#!9/48a3f3/4 and a non-working LEFT JOIN I thought would be equivalent.
Thanks!

Try this, seems to be working if understood the question properly:
SELECT *
FROM `table` t
LEFT JOIN `table` tt ON tt.uniqueID = t.uniqueID AND tt.foreignKeyID <> 1
WHERE t.foreignKeyID = 1 AND tt.id IS NULL;

If mail message doesn't exist, add to mysql database [duplicate]

This question already has answers here:
How can I do 'insert if not exists' in MySQL?
(11 answers)
Closed 2 years ago.
I am trying to execute the following query:
INSERT INTO table_listnames (name, address, tele)
VALUES ('Rupert', 'Somewhere', '022')
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name='value'
);
But this returns an error. Basically I don't want to insert a record if the 'name' field of the record already exists in another record - how to check if the new name is unique?

I'm not actually suggesting that you do this, as the UNIQUE index as suggested by Piskvor and others is a far better way to do it, but you can actually do what you were attempting:
CREATE TABLE `table_listnames` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`address` varchar(255) NOT NULL,
`tele` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
Insert a record:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
Try to insert the same record again:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
Insert a different record:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'John', 'Doe', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'John'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
+----+--------+-----------+------+
And so on...
Update:
To prevent #1060 - Duplicate column name error in case two values may equal, you must name the columns of the inner SELECT:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Unknown' AS name, 'Unknown' AS address, '022' AS tele) AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+---------+-----------+------+
| id | name | address | tele |
+----+---------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
| 3 | Unknown | Unknown | 022 |
+----+---------+-----------+------+

INSERT doesn't allow WHERE in the syntax.
What you can do: create a UNIQUE INDEX on the field which should be unique (name), then use either:
normal INSERT (and handle the error if the name already exists)
INSERT IGNORE (which will fail silently cause a warning (instead of error) if name already exists)
INSERT ... ON DUPLICATE KEY UPDATE (which will execute the UPDATE at the end if name already exists, see documentation)

Worked :
INSERT INTO users (full_name, login, password)
SELECT 'Mahbub Tito','tito',SHA1('12345') FROM DUAL
WHERE NOT EXISTS
(SELECT login FROM users WHERE login='tito');

MySQL provides a very cute solution :
REPLACE INTO `table` VALUES (5, 'John', 'Doe', SHA1('password'));
Very easy to use since you have declared a unique primary key (here with value 5).

INSERT IGNORE INTO `mytable`
SET `field0` = '2',
`field1` = 12345,
`field2` = 12678;
Here the mysql query, that insert records if not exist and will ignore existing similar records.
----Untested----

You can easily use the following way :
INSERT INTO ... ON DUPLICATE KEY UPDATE ...
In this way, you can insert any new raw and if you have duplicate data, replace a specific column ( The best columns are timestamps ).
For example :
CREATE TABLE IF NOT EXISTS Devices (
id INT(6) NOT NULL AUTO_INCREMENT,
unique_id VARCHAR(100) NOT NULL PRIMARY KEY,
created_at VARCHAR(100) NOT NULL,
UNIQUE KEY unique_id (unique_id),
UNIQUE KEY id (id)
)
CHARACTER SET utf8
COLLATE utf8_unicode_ci;
INSERT INTO Devices(unique_id, time)
VALUES('$device_id', '$current_time')
ON DUPLICATE KEY UPDATE time = '$current_time';

To overcome a similar problem, I have modified the table to have a unique column. Using your example, on creation I would have something like:
name VARCHAR(20),
UNIQUE (name)
and then use the following query when inserting into it:
INSERT IGNORE INTO train
set table_listnames='Rupert'

If you really can't get a unique index on the table, you could try...
INSERT INTO table_listnames (name, address, tele)
SELECT 'Rupert', 'Somewhere', '022'
FROM some_other_table
WHERE NOT EXISTS (SELECT name
FROM table_listnames
WHERE name='Rupert')
LIMIT 1;

This query works well:
INSERT INTO `user` ( `username` , `password` )
SELECT * FROM (SELECT 'ersks', md5( 'Nepal' )) AS tmp
WHERE NOT EXISTS (SELECT `username` FROM `user` WHERE `username` = 'ersks'
AND `password` = md5( 'Nepal' )) LIMIT 1
And you can create the table using following query:
CREATE TABLE IF NOT EXISTS `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(30) NOT NULL,
`password` varchar(32) NOT NULL,
`status` tinyint(1) DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
Note: Create table using second query before trying to use first query.

Brian Hooper :
You almost hit the point but you have an error in your synatx. Your insert will never work. I tested on my database and here is the right answer:
INSERT INTO podatki (datum,ura,meritev1,meritev1_sunki,impulzi1,meritev2,meritev2_sunki,impulzi2)
SELECT '$datum', '$ura', '$meritve1','$sunki1','$impulzi1','$meritve2','$sunki2','$impulzi2'
FROM dual
WHERE NOT EXISTS (SELECT datum,ura
FROM podatki
WHERE datum='$datum' and ura='$ura'
I'm giving you my example of y table. Insert is almost the same like Bian Hooper wrote, except that I put the select FROM DUAL ont from other table.
Cind regards, Ivan

This is not an answer, it's just a note. The query like the one in the accepted answer does not work if the inserted values are duplicates, like here:
INSERT INTO `addr` (`email`, `name`)
SELECT * FROM (SELECT 'user#domain.tld', 'user#domain.tld') AS tmp
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user#domain.tld'
);
Error
SQL query: Copy Documentation
MySQL said: Documentation
#1060 - Duplicate column name 'user#domain.tld'
In the contrary, the query like the one from Mahbub Tito's answer works fine:
INSERT INTO `addr` (`email`, `name`)
SELECT 'user#domain.tld', 'user#domain.tld'
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user#domain.tld'
);
1 row inserted.
Tested in MariaDB

insert into customer_keyskill(customerID, keySkillID)
select 2,1 from dual
where not exists (
select customerID from customer_keyskill
where customerID = 2
and keySkillID = 1 )

You are inserting not Updating the result.
You can define the name column in primary column or set it is unique.

I had a problem, and the method Mike advised worked partly, I had an error Dublicate Column name = '0', and changed the syntax of your query as this`
$tQ = "INSERT INTO names (name_id, surname_id, sum, sum2, sum3,sum4,sum5)
SELECT '$name', '$surname', '$sum', '$sum2', '$sum3','$sum4','$sum5'
FROM DUAL
WHERE NOT EXISTS (
SELECT sum FROM names WHERE name_id = '$name'
AND surname_id = '$surname') LIMIT 1;";
The problem was with column names. sum3 was equal to sum4 and mysql throwed dublicate column names, and I wrote the code in this syntax and it worked perfectly,

I had a similar problem and I needed to insert multiple if not existing. So from the examples above I came to this combination... it's here just in case somebody would need it.
Notice:
I had to define name everywhere as MSSQL required it... MySQL works with * too.
INSERT INTO names (name)
SELECT name
FROM
(
SELECT name
FROM
(
SELECT 'Test 4' as name
) AS tmp_single
WHERE NOT EXISTS
(
SELECT name FROM names WHERE name = 'Test 4'
)
UNION ALL
SELECT name
FROM
(
SELECT 'Test 5' as name
) AS tmp_single
WHERE NOT EXISTS
(
SELECT name FROM names WHERE name = 'Test 5'
)
) tmp_all;
MySQL:
CREATE TABLE names (
OID int(11) NOT NULL AUTO_INCREMENT,
name varchar(32) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (OID),
UNIQUE KEY name_UNIQUE (name)
) ENGINE=InnoDB AUTO_INCREMENT=1;
or
MSSQL:
CREATE TABLE [names] (
[OID] INT IDENTITY (1, 1) NOT NULL,
[name] NVARCHAR (32) NOT NULL,
PRIMARY KEY CLUSTERED ([OID] ASC)
);
CREATE UNIQUE NONCLUSTERED INDEX [Index_Names_Name] ON [names]([name] ASC);

This query can be used in PHP code.
I have an ID column in this table, so I need check for duplication for all columns except this ID column:
#need to change values
SET #goodsType = 1, #sybType=5, #deviceId = asdf12345SDFasdf2345;
INSERT INTO `devices` (`goodsTypeId`, `goodsId`, `deviceId`) #need to change tablename and columnsnames
SELECT * FROM (SELECT #goodsType, #sybType, #deviceId) AS tmp
WHERE NOT EXISTS (
SELECT 'goodsTypeId' FROM `devices` #need to change tablename and columns names
WHERE `goodsTypeId` = #goodsType
AND `goodsId` = #sybType
AND `deviceId` = #deviceId
) LIMIT 1;
and now new item will be added only in case of there is not exist row with values configured in SET string

creating table from two different table

I am creating table from two different table with query:
create table post_table as
( select t1.id, t2.url, t2.desc, t2.preview, t2.img_url,
t2.title, t2.hash, t2.rate
from user_record t1, post_data t2
primary key (t1.id, t2,hash))
what's syntax error here?
post_data
----
url varchar(255) No
desc varchar(2048) No
preview varchar(255) No
img_url varchar(128) No
title varchar(128) No
hash varchar(128) No // This is one
rate varchar(20) Yes NULL
user_record
id varchar(40) No //This is 2nd
name varchar(50) Yes NULL
email varchar(50) Yes NULL
picture varchar(50) No
UPDATE:
create table post_table (
id VARCHAR(40), url varchar(255), preview varchar(255) , img_url varchar(128), title varchar(128), hash varchar(128), rate varchar(20)
primary key (t1.id, t2,hash));
select t1.id, t2.url, t2.desc, t2.preview, t2.img_url,
t2.title, t2.hash, t2.rate
from user_record t1, post_data t2;

Formatting the CREATE TABLE statement so we can see the ( ) pairing:
create table post_table as (
select t1.id, t2.url, t2.desc, t2.preview, t2.img_url, t2.title, t2.hash, t2.rate
from user_record t1, post_data t2
primary key (t1.id, t2,hash)
)
We can see that the primary key is being attached to the select statement.
Beyond that there are specific restrictions around general CREATE TABLE syntax can be used in a CREATE TABLE ... SELECT statement.
From: http://dev.mysql.com/doc/refman/5.1/en/create-table-select.html
The ENGINE option is part of the CREATE TABLE statement, and should
not be used following the SELECT; this would result in a syntax error.
The same is true for other CREATE TABLE options such as CHARSET.
You can how ever select keys by using syntax similar to:
mysql> CREATE TABLE test (a INT NOT NULL AUTO_INCREMENT,
-> PRIMARY KEY (a), KEY(b))
-> ENGINE=MyISAM SELECT b,c FROM test2;
So with your query re-work it to define the column types first, then the keys, then the select statement last. We don't know your data types but it would look something similar to:
create table post_table (
id DATATYPE, url DATATYPE, desc DATATYPE...
primary key (t1.id, t2,hash))
)
select t1.id, t2.url, t2.desc, t2.preview, t2.img_url,
t2.title, t2.hash, t2.rate
from user_record t1, post_data t2

You have put key definition BEFORE select.
Also you can't do key definition without fields, so if you need keys, you have put all table structure.
http://dev.mysql.com/doc/refman/5.1/en/create-table.html
Other way is create index after creating table by use CREATE INDEX

adding unique values to existing table in mySql

Good Day
I created a table, NEW_TABLE, from some of another table columns ,OLD_TABLE.
I added a new column ID of type double
I want to fill the values of the ID column with unique values and then make it the the NEW_TABLE key.
Is there a way to do this in MySQL with a query or a set command?
I tried something like this:
Insert into NEW_TABLE
(select generateId() , col1, col2
from ORIGINAL_TABLE)

Usually you set the field to be an auto increment field when it is defined. To do so afterwards, you can use:
ALTER TABLE NEW_TABLE MODIFY ID int(10) unsigned NOT NULL auto_increment;
To then insert an new record and for it to automatically get an assigned ID, merely omit the field from the insert.

try this:
Insert into NEW_TABLE
(select #row := #row + 1 as generateId, col1, col2
from ORIGINAL_TABLE, (SELECT #row := 0)row)

You should use autoincrement and an integer field (is there any reason for you to want a double key there?):
CREATE TABLE NEW_TABLE (
id INT NOT NULL AUTO_INCREMENT,
col1 CHAR(30) NOT NULL,
col2 CHAR(30) NOT NULL,
PRIMARY KEY (id)
)

Why did you choose DOUBLE and not an integer datatype?
ALTER TABLE NEW_TABLE
MODIFY ID INT UNSIGNED NOT NULL AUTO_INCREMENT ;
ALTER TABLE NEW_TABLE
ADD CONSTRAINT new_table_pk
PRIMARY KEY (ID) ;
and then:
INSERT INTO NEW_TABLE
(col1, col2)
SELECT col1, col2
FROM ORIGINAL_TABLE ;

MySQL: Insert record if not exists in table [duplicate]

This question already has answers here:
How can I do 'insert if not exists' in MySQL?
(11 answers)
Closed 2 years ago.
I am trying to execute the following query:
INSERT INTO table_listnames (name, address, tele)
VALUES ('Rupert', 'Somewhere', '022')
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name='value'
);
But this returns an error. Basically I don't want to insert a record if the 'name' field of the record already exists in another record - how to check if the new name is unique?

I'm not actually suggesting that you do this, as the UNIQUE index as suggested by Piskvor and others is a far better way to do it, but you can actually do what you were attempting:
CREATE TABLE `table_listnames` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(255) NOT NULL,
`address` varchar(255) NOT NULL,
`tele` varchar(255) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;
Insert a record:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
Try to insert the same record again:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Rupert', 'Somewhere', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
+----+--------+-----------+------+
Insert a different record:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'John', 'Doe', '022') AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'John'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+--------+-----------+------+
| id | name | address | tele |
+----+--------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
+----+--------+-----------+------+
And so on...
Update:
To prevent #1060 - Duplicate column name error in case two values may equal, you must name the columns of the inner SELECT:
INSERT INTO table_listnames (name, address, tele)
SELECT * FROM (SELECT 'Unknown' AS name, 'Unknown' AS address, '022' AS tele) AS tmp
WHERE NOT EXISTS (
SELECT name FROM table_listnames WHERE name = 'Rupert'
) LIMIT 1;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0
SELECT * FROM `table_listnames`;
+----+---------+-----------+------+
| id | name | address | tele |
+----+---------+-----------+------+
| 1 | Rupert | Somewhere | 022 |
| 2 | John | Doe | 022 |
| 3 | Unknown | Unknown | 022 |
+----+---------+-----------+------+

INSERT doesn't allow WHERE in the syntax.
What you can do: create a UNIQUE INDEX on the field which should be unique (name), then use either:
normal INSERT (and handle the error if the name already exists)
INSERT IGNORE (which will fail silently cause a warning (instead of error) if name already exists)
INSERT ... ON DUPLICATE KEY UPDATE (which will execute the UPDATE at the end if name already exists, see documentation)

Worked :
INSERT INTO users (full_name, login, password)
SELECT 'Mahbub Tito','tito',SHA1('12345') FROM DUAL
WHERE NOT EXISTS
(SELECT login FROM users WHERE login='tito');

MySQL provides a very cute solution :
REPLACE INTO `table` VALUES (5, 'John', 'Doe', SHA1('password'));
Very easy to use since you have declared a unique primary key (here with value 5).

INSERT IGNORE INTO `mytable`
SET `field0` = '2',
`field1` = 12345,
`field2` = 12678;
Here the mysql query, that insert records if not exist and will ignore existing similar records.
----Untested----

You can easily use the following way :
INSERT INTO ... ON DUPLICATE KEY UPDATE ...
In this way, you can insert any new raw and if you have duplicate data, replace a specific column ( The best columns are timestamps ).
For example :
CREATE TABLE IF NOT EXISTS Devices (
id INT(6) NOT NULL AUTO_INCREMENT,
unique_id VARCHAR(100) NOT NULL PRIMARY KEY,
created_at VARCHAR(100) NOT NULL,
UNIQUE KEY unique_id (unique_id),
UNIQUE KEY id (id)
)
CHARACTER SET utf8
COLLATE utf8_unicode_ci;
INSERT INTO Devices(unique_id, time)
VALUES('$device_id', '$current_time')
ON DUPLICATE KEY UPDATE time = '$current_time';

To overcome a similar problem, I have modified the table to have a unique column. Using your example, on creation I would have something like:
name VARCHAR(20),
UNIQUE (name)
and then use the following query when inserting into it:
INSERT IGNORE INTO train
set table_listnames='Rupert'

If you really can't get a unique index on the table, you could try...
INSERT INTO table_listnames (name, address, tele)
SELECT 'Rupert', 'Somewhere', '022'
FROM some_other_table
WHERE NOT EXISTS (SELECT name
FROM table_listnames
WHERE name='Rupert')
LIMIT 1;

This query works well:
INSERT INTO `user` ( `username` , `password` )
SELECT * FROM (SELECT 'ersks', md5( 'Nepal' )) AS tmp
WHERE NOT EXISTS (SELECT `username` FROM `user` WHERE `username` = 'ersks'
AND `password` = md5( 'Nepal' )) LIMIT 1
And you can create the table using following query:
CREATE TABLE IF NOT EXISTS `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(30) NOT NULL,
`password` varchar(32) NOT NULL,
`status` tinyint(1) DEFAULT '0',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
Note: Create table using second query before trying to use first query.

Brian Hooper :
You almost hit the point but you have an error in your synatx. Your insert will never work. I tested on my database and here is the right answer:
INSERT INTO podatki (datum,ura,meritev1,meritev1_sunki,impulzi1,meritev2,meritev2_sunki,impulzi2)
SELECT '$datum', '$ura', '$meritve1','$sunki1','$impulzi1','$meritve2','$sunki2','$impulzi2'
FROM dual
WHERE NOT EXISTS (SELECT datum,ura
FROM podatki
WHERE datum='$datum' and ura='$ura'
I'm giving you my example of y table. Insert is almost the same like Bian Hooper wrote, except that I put the select FROM DUAL ont from other table.
Cind regards, Ivan

This is not an answer, it's just a note. The query like the one in the accepted answer does not work if the inserted values are duplicates, like here:
INSERT INTO `addr` (`email`, `name`)
SELECT * FROM (SELECT 'user#domain.tld', 'user#domain.tld') AS tmp
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user#domain.tld'
);
Error
SQL query: Copy Documentation
MySQL said: Documentation
#1060 - Duplicate column name 'user#domain.tld'
In the contrary, the query like the one from Mahbub Tito's answer works fine:
INSERT INTO `addr` (`email`, `name`)
SELECT 'user#domain.tld', 'user#domain.tld'
WHERE NOT EXISTS (
SELECT `email` FROM `addr` WHERE `email` LIKE 'user#domain.tld'
);
1 row inserted.
Tested in MariaDB

insert into customer_keyskill(customerID, keySkillID)
select 2,1 from dual
where not exists (
select customerID from customer_keyskill
where customerID = 2
and keySkillID = 1 )

You are inserting not Updating the result.
You can define the name column in primary column or set it is unique.

I had a problem, and the method Mike advised worked partly, I had an error Dublicate Column name = '0', and changed the syntax of your query as this`
$tQ = "INSERT INTO names (name_id, surname_id, sum, sum2, sum3,sum4,sum5)
SELECT '$name', '$surname', '$sum', '$sum2', '$sum3','$sum4','$sum5'
FROM DUAL
WHERE NOT EXISTS (
SELECT sum FROM names WHERE name_id = '$name'
AND surname_id = '$surname') LIMIT 1;";
The problem was with column names. sum3 was equal to sum4 and mysql throwed dublicate column names, and I wrote the code in this syntax and it worked perfectly,

I had a similar problem and I needed to insert multiple if not existing. So from the examples above I came to this combination... it's here just in case somebody would need it.
Notice:
I had to define name everywhere as MSSQL required it... MySQL works with * too.
INSERT INTO names (name)
SELECT name
FROM
(
SELECT name
FROM
(
SELECT 'Test 4' as name
) AS tmp_single
WHERE NOT EXISTS
(
SELECT name FROM names WHERE name = 'Test 4'
)
UNION ALL
SELECT name
FROM
(
SELECT 'Test 5' as name
) AS tmp_single
WHERE NOT EXISTS
(
SELECT name FROM names WHERE name = 'Test 5'
)
) tmp_all;
MySQL:
CREATE TABLE names (
OID int(11) NOT NULL AUTO_INCREMENT,
name varchar(32) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (OID),
UNIQUE KEY name_UNIQUE (name)
) ENGINE=InnoDB AUTO_INCREMENT=1;
or
MSSQL:
CREATE TABLE [names] (
[OID] INT IDENTITY (1, 1) NOT NULL,
[name] NVARCHAR (32) NOT NULL,
PRIMARY KEY CLUSTERED ([OID] ASC)
);
CREATE UNIQUE NONCLUSTERED INDEX [Index_Names_Name] ON [names]([name] ASC);

This query can be used in PHP code.
I have an ID column in this table, so I need check for duplication for all columns except this ID column:
#need to change values
SET #goodsType = 1, #sybType=5, #deviceId = asdf12345SDFasdf2345;
INSERT INTO `devices` (`goodsTypeId`, `goodsId`, `deviceId`) #need to change tablename and columnsnames
SELECT * FROM (SELECT #goodsType, #sybType, #deviceId) AS tmp
WHERE NOT EXISTS (
SELECT 'goodsTypeId' FROM `devices` #need to change tablename and columns names
WHERE `goodsTypeId` = #goodsType
AND `goodsId` = #sybType
AND `deviceId` = #deviceId
) LIMIT 1;
and now new item will be added only in case of there is not exist row with values configured in SET string