转换为base64才可以
PostgreSQL
SELECT encode(blob_column, 'base64') AS base64_column FROM my_table;
mysql
SELECT TO_BASE64(BLOB_COLUMN) FROM MY_TABLE;
Oracle:
Oracle没有直接提供将BLOB转换为Base64的内置函数,但可以使用UTL_ENCODE包来实现
SELECT UTL_ENCODE.BASE64_ENCODE(UTL_RAW.CAST_TO_VARCHAR2(BLOB_COLUMN)) AS BASE64_DATA
FROM BLOB_TEST;