How Does String Concatenation Work in Oracle SQL?

String concatenation in Oracle SQL

String concatenation, the operation of concatenating multiple strings into a single string, is a basic operation in any programming language. In Oracle SQL, this task is accomplished using the join operator ||.

Grammar

The syntax for string concatenation in Oracle SQL is very simple:

<code class="language-sql">字符串表达式 || 字符串表达式</code>

Where each string expression represents a string or a value that can be converted to a string.

Example

The following query joins the title "Mr." with the employee names in the emp table:

<code class="language-sql">SELECT 'Mr. ' || ename FROM emp;</code>

Notes

It is important to note that when concatenated with null values, Oracle treats them as non-null values. This means 'x' || null will return 'x', not null. This behavior may be unexpected and may require additional handling in your code.

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