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What is the difference between UNION and UNION ALL? Select the correct answer from above options

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UNION: This command is used to select the tuples which have related information from two or more tables. Are you interested in learning SQL from scratch! Have a look at this interesting video on SQL provided by Intellipaat: If you understand by watching videos, here’s the informative video about UNION It’s similar to JOIN command. But when we are using UNION command, the selected columns must be of the same data type. It removes all the duplicate records from the final result. Syntax Select Column1, Column2, Column3 from Table A UNION Select Column1, Column2, Column3 from Table B Example: There are two tables named Student and Teacher TABLE 1: Student StudentID StudName StudentAge 1 Bhumi 16 2 Manas 17 3 Mallik 18 4 Suraj 15 5 Raj 15.5 TABLE 2: Teacher TeacherID TeachName TeacherAge 1 Betty 28 2 Mallik 29 3 James 45 4 Suraj 30 Query: SELECT StudName FROM Student UNION SELECT TeachName FROM Teacher NO StudName 1 Bhumi 2 Betty 3 James 4 Manas 5 Mallik 6 Raj 7 Suraj Here, you can see the duplicate tuples are removed. UNION ALL: This command is the same as UNION command. It just concatenates the records. Unlike UNION, UNION ALL pulls all the values from all the tables i.e. it doesn’t eliminate duplicate records. Syntax Select Column1, Column2, Column3 from Table A UNION Select Column1, Column2, Column3 from Table B Example: Consider the above two tables Student and Teacher. Query: Select Column1, Column2, Column3 from Table A UNION ALL Select Column1, Column2, Column3 from Table B NO StudName 1 Bhumi 2 Manas 3 Mallik 4 Suraj 5 Raj 6 Betty 7 Mallik 8 James 9 Suraj You can observer here, the result is a combination of both the tables. UNION vs UNION ALL The only difference between Union and Union All is that Union All will not removes duplicate rows or records, instead, it just selects all the rows from all the tables which meets the conditions of your specifics query and combines them into the result table. UNION doesn’t work with a column that has Text Data Type. Whereas, UNION ALL works with all data type columns.

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