BYTE vs. CHAR in Oracle VARCHAR2: What's the Difference in Data Storage?

Oracle VARCHAR2: BYTE vs. CHAR – A Crucial Data Storage Distinction

Efficient Oracle database design hinges on understanding the nuances of BYTE and CHAR when defining VARCHAR2 columns. This article clarifies their key differences for optimal data handling.

When specifying the length of a VARCHAR2 column, you use either BYTE or CHAR. BYTE sets the maximum number of bytes allocated, while CHAR sets the maximum number of characters.

Consider these table definitions:

CREATE TABLE CLIENT
(
 NAME VARCHAR2(11 BYTE),
 ID_CLIENT NUMBER
)

CREATE TABLE CLIENT
(
 NAME VARCHAR2(11 CHAR), -- or VARCHAR2(11)
 ID_CLIENT NUMBER
)

In the first example, Oracle reserves 11 bytes for the NAME column. Given that modern Oracle uses UTF-8 encoding (by default), multi-byte characters (common in non-English languages) might exceed the 11-byte limit, potentially truncating data.

The second example, however, guarantees enough space for 11 characters, regardless of their byte size (up to 4 bytes per character in UTF-8).

Therefore, VARCHAR2(11 CHAR) ensures sufficient space for the specified character count, while VARCHAR2(11 BYTE) limits storage by bytes, not characters. This is vital for multilingual data or data containing special characters. Choosing the right data type is essential for both storage efficiency and data integrity.

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