{"id":244,"date":"2024-08-23T02:07:43","date_gmt":"2024-08-23T02:07:43","guid":{"rendered":"https:\/\/techkubo.com\/sql\/?p=244"},"modified":"2025-05-13T13:25:53","modified_gmt":"2025-05-13T13:25:53","slug":"sql-union","status":"publish","type":"post","link":"https:\/\/techkubo.com\/sql\/sql-union\/","title":{"rendered":"SQL Union"},"content":{"rendered":"\n

In SQL, the UNION operator is used to combine the results of two or more SELECT queries into a single result set. The key thing to remember is that each SELECT statement within the UNION must have the same number of columns, with similar data types in the correspoding columns.<\/p>\n\n\n\n

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SQL Union Syntax<\/h2>\n\n\n\n
SELECT column1, column2, ...\nFROM table1\nUNION\nSELECT column1, column2, ...\nFROM table2;<\/pre><\/div>\n\n\n\n
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SQL Union Basic Example<\/h2>\n\n\n\n
This query will return a list of distinct first names from both Patients and Doctors tables.<\/p>\n\n\n\n
SELECT first_name FROM Patients\nUNION\nSELECT first_name FROM Doctors;<\/pre><\/div>\n\n\n\n
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Try It Out!<\/a><\/div>\n<\/div>\n\n\n\n
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SQL Union ALL Example<\/h3>\n\n\n\n
This query returns all the first names, including duplicates, from both tables. For example, if a first name appears in both tables, it will be listed twice.<\/p>\n\n\n\n
SELECT first_name FROM Patients\nUNION ALL\nSELECT first_name FROM Doctors;<\/pre><\/div>\n\n\n\n
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SQL Union with WHERE Example<\/h3>\n\n\n\n
This query will return a list of distinct first names, combining female patients from the Patients table and pediatric doctors from the Doctors table.<\/p>\n\n\n\n
SELECT first_name FROM Patients WHERE gender = 'F'\nUNION\nSELECT first_name FROM Doctors WHERE specialty = 'Pediatrics';<\/pre><\/div>\n\n\n\n
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SQL Union ALL with WHERE Example<\/h3>\n\n\n\n
This query returns all male patients and all doctors who specialize in cardiology. It will include duplicates if a first name appears in both groups.<\/p>\n\n\n\n
SELECT first_name FROM Patients WHERE gender = 'M'\nUNION ALL\nSELECT first_name FROM Doctors WHERE specialty = 'Cardiology';<\/pre><\/div>\n\n\n\n
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SQL Union Another Union Example<\/h3>\n\n\n\n
This query combines last names from the Patients and Doctors tables and names from the Students table.<\/p>\n\n\n\n
SELECT last_name FROM Patients\nUNION\nSELECT last_name FROM Doctors\nUNION\nSELECT name FROM Students;<\/pre><\/div>\n\n\n\n
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SQL Union Visual Diagram<\/h2>\n\n\n\n
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SQL Union Labs<\/h2>\n\n\n\n