Combining Results of Two or More Queries. Summary in this tutorial, you will learn how to use My. SQL UNION operator to combine two or more result sets from multiple SELECT statements into a single result set. Mysql Multiple Column Update Query In Mysql In W3schools' title='Mysql Multiple Column Update Query In Mysql In W3schools' />My. SQL UNION operator. My. SQL UNION operator allows you to combine two or more result sets of queries into a single result set. The following illustrates the syntax of the UNION operator. Mysql Multiple Column Update Query In Mysql Example' title='Mysql Multiple Column Update Query In Mysql Example' />SELECT columnlist. UNION DISTINCT ALL. SELECT columnlist. To combine result set of two or more queries using the UNION operator, there are the basic rules that you must follow First, the number and the orders of columns that appear in all SELECT statements must be the same. Second, the data types of columns must be the same or convertible. By default, the UNION operator removes duplicate rows even if you dont specify the DISTINCT operator explicitly. Lets see the following sample tables t. DROP TABLE IF EXISTS t. SELECT can also be used to retrieve rows computed without reference to any table. For example mysql SELECT 1 1 2. Example Update multiple columns. Lets look at a MySQL UPDATE example where you might want to update more than one column with a single UPDATE statement. DROP TABLE IF EXISTS t. CREATE TABLE t. 1. INT PRIMARY KEY. CREATE TABLE t. INT PRIMARY KEY. INSERT INTO t. VALUES 1,2,3. INSERT INTO t. VALUES 2,3,4 INSERTINTOt. I have two tables, both looking like id name value 1 Joe 22 2 Derk 30 I need to copy the value of value from tableA to tableB based on. VALUES1,2,3 INSERTINTOt. VALUES2,3,4 The following statement combines result sets returned from t. FROM t. 2 The final result set contains the distinct values from separate result sets returned by the queries. Because the rows with value 2 and 3 are duplicates, the UNION operator removed it and kept only distinct ones. The following Venn diagram illustrates the union of two result sets that come from t. If you use the UNION ALL explicitly, the duplicate rows, if available, remain in the result. Because UNION ALL does not need to handle duplicates, it performs faster than UNION DISTINCT . As you can see, the duplicates appear in the combined result set because of the UNION ALL operation. UNION vs. JOINA JOIN combines result sets horizontally, a UNION appends result set vertically. The following picture illustrates the difference between UNION and JOIN My. SQL UNION and column alias examples. We will use the customers and employees tables in the sample database for the demonstration  Suppose you want to combine the first name and last name of both employees and customers into a single result set, you can use the UNION operator as follows. Name. contact. First. Mysql Multiple Column Update Query In Mysql Workbench' title='Mysql Multiple Column Update Query In Mysql Workbench' />Mysqlquery sends a unique query multiple queries are not supported to the currently active database on the server thats associated with the specified link. MySQL INDEXES Learn MySQL from basic to advanced covering database programming clauses command functions administration queries and usage along with PHP in simple. Name. contact. Last. Name. customers Here is the output As you can see, the My. SQL UNION operator uses the column names of the first SELECT statement for labeling the columns in the output. If you want to use your own column aliases, you need to specify them explicitly in the first SELECT statement as shown in the following example. Name, ,last. Name fullname. First. Name, ,contact. Last. Name. customers    concatfirst. Name, ,last. Namefullname    concatcontact. First. Name, ,contact. Last. NameIn this example, instead of using the default column label from the first query, we used a column alias  fullname for labeling the output. My. SQL UNION and ORDER BYIf you want to sort the result  of a union, you use an ORDER BY clause in the last SELECT statement as shown in the following example. Name, ,last. Name fullname. First. Name, ,contact. Last. Name. ORDER BY fullname    concatfirst. Name, ,last. Namefullname    concatcontact. First. Name, ,contact. Last. NameNotice that if you place the ORDER BY clause in each SELECT statement, it will not affect the order of the rows in the final result set. My. SQL also provides you with alternative option to sort a result set based on column position using ORDER BY clause as follows. Name, ,last. Name fullname. First. Name, ,contact. Last. Name. ORDER BY 1    concatfirst. Name, ,last. Namefullname    concatcontact. First. Name, ,contact. Last. NameIn this tutorial, you have learned how to use My. SQL UNION statement to combine data from multiple queries into a single result set. 3D Studio Viewer Free Download.