How to concatenate strings in oracle

Oracle provides three methods of splicing strings: connection operator (||), DBMS_LOB.CONCAT()/CONCAT() function. For most cases, the concatenation operator is the most convenient choice, while the DBMS_LOB.CONCAT()/CONCAT() function is recommended for large string concatenation.

Methods of splicing strings in Oracle

Oracle provides a variety of methods to splice strings, including using The join operator (||), the DBMS_LOB.CONCAT() function, and the CONCAT() function.

1. Concatenation operator (||)

This is the simplest method, it simply combines two or more characters Strings are concatenated together to form a new string. The syntax is as follows:

<code>string1 || string2 || ... || stringN</code>

For example:

<code>SELECT 'Hello' || ' ' || 'World' FROM dual;</code>

Result:

<code>Hello World</code>

2. DBMS_LOB.CONCAT() Function

DBMS_LOB.CONCAT() The function is used to concatenate large strings (more than 4000 bytes) and is more efficient than the concatenation operator. The syntax is as follows:

<code>DBMS_LOB.CONCAT(lob1, lob2, ...)</code>

Among them, the lob parameter represents the LOB data type (CLOB or BLOB).

3. CONCAT() Function

CONCAT() The function is DBMS_LOB.CONCAT() Alias ​​for the function, available in Oracle 12c and later. Its syntax is the same as the DBMS_LOB.CONCAT() function.

Example:

<code>SELECT CONCAT('Hello', ' ', 'World') FROM dual;</code>

Result:

<code>Hello World</code>

Which method is best?

In most cases, using the concatenation operator is the simplest and most efficient method. However, if you need to concatenate large strings, you should use the DBMS_LOB.CONCAT() or CONCAT() function.

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