The conditions of the JOIN ON clause in SQL are used to merge tables through comparison conditions between columns. The conditional syntax is: JOIN table2 ON table1.column = table2.column, where the columns must have compatible data types. If the connection type is not specified, INNER JOIN is used by default.
Conditions of JOIN ON clause in SQL
What is JOIN ON clause?
The JOIN ON clause is used to merge two or more tables in a SQL query. It specifies the conditions between the columns of the joined tables.
Conditional syntax
The conditional syntax of the JOIN ON clause is as follows:
JOIN table2 ON table1.column = table2.column
Among them:
-
table1andtable2are the two tables to be joined. -
columnare the two columns to be compared. -
=is a comparison operator.
Conditional Examples
The following are some examples of JOIN ON clause conditions:
JOIN orders ON customers. id = orders.customer_idJOIN products ON categories.id = products.category_idJOIN employees ON departments.id = employees.department_id
Note:
- The columns in the condition must have compatible data types.
- If no JOIN type is specified, INNER JOIN is used by default.
- You can use multiple JOIN ON clauses to join multiple tables.
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