#SQLITE INSERT DUPLICATE TO UNIQUE HOW TO#
#SQLITE INSERT DUPLICATE TO UNIQUE CODE#

The statement returns 11 rows with one NULL value. See the following statement: SELECT DISTINCT company Now, if you apply the DISTINCT clause to the statement, it will keep only one row with a NULL value. It returns 59 rows with many NULL values.

#SQLITE INSERT DUPLICATE TO UNIQUE CODE#

SELECT companyįROM customers Code language: SQL (Structured Query Language) ( sql ) This statement returns the names of companies of customers from the customers table. To remove duplicate the city and country, you apply the DISTINCT clause to both city and country columns as shown in the following query: SELECT DISTINCTĪs mentioned earlier, SQLite uses the combination of city and country to evaluate the duplicate. The result set contains duplicate city and country e.g., Sao Paulo in Brazil as shown in the screenshot above. SELECTĬountry Code language: SQL (Structured Query Language) ( sql ) The following statement finds cities and countries of all customers. SQLite SELECT DISTINCT on multiple columns It returns 53 rows because the DISTINCT clause has removed 6 duplicate rows. There are few duplicate rows such as Berlin London, and Mountain View To remove these duplicate rows, you use the DISTINCT clause as follows: SELECT DISTINCT city ORDER BY city Code language: SQL (Structured Query Language) ( sql ) Suppose you want to know the cities where the customers locate, you can use the SELECT statement to get data from the city column of the customers table as follows: SELECT city We will use the customers table in the sample database for demonstration. In database theory, if a column contains NULL values, it means that we do not have the information about that column of particular records or the information is not applicable.įor example, if a customer has a phone number with a NULL value, it means we don’t have information about the phone number of the customer at the time of recording customer information or the customer may not have a phone number at all. If you use the DISTINCT clause with a column that has NULL values, SQLite will keep one row of a NULL value. SQLite considers NULL values as duplicates. In case you use multiple columns, SQLite uses the combination of values in these columns to evaluate the duplicate.

If you use one column, SQLite uses values in that column to evaluate the duplicate.

Second, you place a column or a list of columns after the DISTINCT keyword.

First, the DISTINCT clause must appear immediately after the SELECT keyword.

The following statement illustrates the syntax of the DISTINCT clause: SELECT DISTINCT select_listįROM table Code language: SQL (Structured Query Language) ( sql ) The DISTINCT clause allows you to remove the duplicate rows in the result set.

The DISTINCT clause is an optional clause of the SELECT statement. Introduction to SQLite SELECT DISTINCT clause

#SQLITE INSERT DUPLICATE TO UNIQUE HOW TO#

There is a great need for a sarcasm font.Summary: in this tutorial, you will learn how to use the SQLite SELECT DISTINCT clause to remove duplicate rows in the result set. I would assume SQLite also uses some kind of a sequence for PK Which hashid value do you use then?Īlso, Access uses something called 'AutoNumber' field as PK for a table, Oracle and SQL Server uses sequences to increment PK value in the tables. Your 'pseudocode' logic may theoretically work if you always insert a record into the emailprops table related to the last record in email table, but is that always the case? You may have 100 records in email table, and you want to insert a record into emailprops table related to the 27th record in email table. But how do you know which record in emailprops table relates to which record in email table before you insert the record into emailprops table? And which hashid value to use as the value for compid in emailprops table? I don't think you can have this logic in the definition of the tables, you need to have it in the code that deals with INSERT INTO emailprops statements. So in order to INSERT any record into emailprops table, you need to have a record in the email table. Well, you have here Parent (email) - Child (emailprops) relationship between the 2 tables.

Sqlite insert duplicate to unique