Let us consider two tables for implementing the query statements using both operators.
Let us evaluate and illustrate some of the examples showing working and results of the MySQL UNION ALL operator in the database upon the related tables: Examples If everything is proper in the UNION ALL query statement then, the result rows are retrieved but it comprises duplicate row values between the several SELECT statements used in the command to make union set of database tables.
#Mysql union code#
This is because to assure that the resultant rows do not mismatch and produce any MySQL code error. Therefore, it fetches the rows from both the tables where each statement with SELECT keyword command must include an identical number of column fields along with the matching data types. As we come to know that the MySQL UNION ALL operator allows combining the result rows of multiple SELECT queries. How does UNION ALL Operator work in MySQL? The number of Column fields must be identical for each SELECT query included and the statement must consist of at least a single table mentioned with the FROM clause. WHERE condition is an optional matching expression to be used for the SELECT statement fields in the tables provided. The Col_expr1, Col_expr2,…, Col_exprN is the expressional column values that are required to be fetched from two or more tables likeTableName_A or TableName_B. Here, let us explain the parameters listed above: Hadoop, Data Science, Statistics & others SELECT Col_expr1, Col_expr2,…,Col_exprN FROM TableName_B SELECT Col_expr1, Col_expr2,…,Col_exprN FROM TableName_A The MySQL UNION operator performs to give the distinctive values of set in the result after the union of the result rows of SELECT statements whereas the MySQL UNION ALL operator allows the union producing the result set from SELECT statements having replica values in the records fetched from the database tables where it is applied.įollowing is the elementary syntax code for the usage of MySQL UNION ALL operator with the SELECT statements to shows the combination of table values having similar field and data types:. But there is slightly a difference in their work which makes them two different commands used in MySQL for their respective purposes. Like, MySQL UNION operator it is also a useful command in MySQL database to combine more than two of the output set provided by the use of SELECT queries. MySQL UNION ALL operator is a union query command which syndicates multiple SELECT statements’ results into a single result row.
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