![]() To learn how to switch between the two query formats you can read this blog post. Using data from the table above, we have an example query on how to run the query in Standard SQL presented below. You must add the following UNION keywords that follow the UNION operator which is: ALL or DISTINCT. Standard SQL: The new method takes longer, but is more familiar and, therefore, more user-friendly when using Google BigQuery.Using data from the table above, we have an example query on how to run the query in Legacy SQL presented below. All you need is a comma-separated list of the many tables included inside the FROM clause. Comma-Delimited UNIONS in Legacy SQL: With this method, merging data is very easy.There are two main ways to unite results with UNION in BigQuery which is:Ĭomma-Delimited UNIONS in Legacy SQL and Standard SQL. Returns specific records from queries and tablesĪll queries and tables data are returned. BigQuery UNION vs UNION ALL UNION DISTINCT The UNION DISTINCT discards all repeated values. To get all the Names from the two tables above using UNION DISTINCT, our query will be: SELECT Name FROM ``įrom the query above, we ended up with the final table containing a combined result set of Names with duplicates ignored from the Sales and Customers tables. Note: The UNION DISTINCT in BigQuery is equivalent to UNION in SQL. The UNION DISTINCT unites and discards duplicate items from the result sets of two or more input queries. The UNION ALL also returns duplicate values. SELECT Name FROM ``įrom the query above, we ended up with the final table containing a combined result set of Names from the Sales and Customers tables. Now, to further explain this, if we want to get all the Names from the two tables above using UNION ALL, our query will be: SELECT Name FROM `` This leads to the UNION ALL being superior to the UNION DISTINCT in terms of performance. When you execute a UNION ALL query on BigQuery, all input values are returned however, when you perform a UNION DISTINCT query, only unique records are returned. The second table we have here is the Sales table BigQuery UNION ALL ![]() The first table we have here is the Customers table ![]() At least one table must be specified.Īs an example, let’s consider the following tables and how they can be combined using UNION in BigQuery. Tables: The tables containing the records you want to query.Column name: The columns you want to get records from.When executing a UNION query, all the data received from each query is combined, and repeated values are either removed or returned depending on the keyword applied.Ī graphical description of the UNION operator: Union in BigQuery syntax SELECT column name, column name.FROM table1 The only requirement is that BigQuery UNION is used with the “ALL” or “DISTINCT” keywords. If you’ve ever dealt with UNION queries in SQL, you’ll be familiar with BigQuery UNION queries. Rules on how to use UNION in BigQuery What does UNION mean in BigQuery?Ĭombining the results of two or more queries in a vertical manner by consolidating or unifying the columns from the result sets of each query is what UNION in BigQuery is all about.
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