![]() ![]() For example: if you have column1 as STRING, then column3 should be STRING as well (or STRING. Column name and data types: It’s important to understand that the columns that we want to combine should have the same or compatible data type. ![]() In that case, you can use the aliases to temporarily give a different name to the output column. We can see that it is possible to combine multiple SELECT queries with UNION to get the resulting row set. In MySQL, when you use the SQL function to generate a customized output the name of the output column might not be human readable or very difficult to understand. +-+-+-+Īs you can see how much typing effort we can save by using the table aliases.Ĭheck out the SQL JOINS section to learn more about table joins. Each column gets assigned a single name. Using aliases you can make column names more readable. (Its not possible to specify two different aliases for one column in the resultset. In MySQL Aliases are usually used to give a temporary name to table, or a column. The column names and aliases in subsquent queries are ignored. If you execute any of these statements, you'll get the same output, as follow: With a UNION and UNION ALL set operators, the column names for the resultset are specified in the first SELECT. ON t1.dept_id = t2.dept_id ORDER BY emp_id Select the table name as a column in a UNION select query in MySQL. So the first column will be either called 'User' or 'setting' or 'currency', but never the right value'. Example Try this code » SELECT t1.emp_id, t1.emp_name, t2.dept_nameįROM employees AS t1 LEFT JOIN departments AS t2 You clearly want to retrieve both settings and currencies and distinguish them, but since you run one select, any column will only have one name. ![]()
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