To solve this issue, we should exclude last_update from the 2 tables, so that rows will be matched using only the customer_id. Lesson learned: using NATURAL JOIN requires carefulness. MySQL union is a function to combine two table's data on a single page.The union in MySQL removes duplicate rows from the tables and returns unique data in a result set. Sometimes, you require multiple tables to collect data together. Each subclause provides a subquery that produces a result set, and associates a name with the subquery. 09:43:21 MySQL Union MySQL contains the same categories of data in a different table. Thus, when NATURAL JOIN joins these 2 tables, it requires both customer_id and last_update be equal for 2 rows to be matched, and of course, no pair of rows satisfies this criterion. To specify common table expressions, use a WITH clause that has one or more comma-separated subclauses. Run SQL » Result: Click 'Run SQL' to execute the SQL statement above. This is because, in this Pagila database, every table has a column named last_update. SQL Statement: x SELECT City, Country FROM Customers WHERE CountryGermany UNION SELECT City, Country FROM Suppliers WHERE CountryGermany ORDER BY City Edit the SQL Statement, and click 'Run SQL' to see the result. However, the result shows no rows at all. Let’s take some examples of using the PostgreSQL UNION operator. Every SELECT statement within UNION must have the same number of columns. Normally, this query will work: SELECT *įROM customer NATURAL JOIN rental customer_id The UNION operator is used to combine the result-set of two or more SELECT statements.
These 2 tables have a common column: customer_id. UNION combines the result from multiple SELECT statements into a single result set. Get all information from a natural (inner) join of the customer and rental tables.
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