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POWhy does Oracle require TO_NCHAR when binding SQL_C_WCHAR text via ODBC
 

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  1. POWhy does Oracle require TO_NCHAR when binding SQL_C_WCHAR text via ODBC
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    <p>I use the following statement prepared and bound in ODBC:</p> <pre><code>SELECT (CASE profile WHEN ? THEN 1 ELSE 2 END) AS profile_order FROM engine_properties; </code></pre> <p>Executed in an ODBC 3.0 connection to an Oracle 10g database in AL32UTF8 charset, even after binding to a wchar_t string using <code>SQLBindParameter(SQL_C_WCHAR)</code>, it still gives the error ORA-12704: character set mismatch. </p> <p>Why? I'm binding as wchar. Shouldn't a wchar be considered an NCHAR? </p> <p>If I change the parameter to wrap it with <code>TO_NCHAR()</code> then the query works without error. However since these queries are used for multiple database backends, I don't want to add TO_NCHAR just on Oracle text bindings. Is there something that I am missing? Another way to solve this without the TO_NCHAR hammer?</p> <p>I haven't been able to find anything relevant via searches or in the manuals.</p> <p>More details...</p> <p>-- error</p> <pre><code>SELECT (CASE profile WHEN '_default' THEN 1 ELSE 2 END) AS profile_order FROM engine_properties; </code></pre> <p>-- ok</p> <pre><code>SELECT (CASE profile WHEN TO_NCHAR('_default') THEN 1 ELSE 2 END) AS profile_order FROM engine_properties; </code></pre> <pre> SQL> describe engine_properties; Name Null? Type ----------------------------------------- -------- ---------------------------- EID NOT NULL NVARCHAR2(22) LID NOT NULL NUMBER(11) PROFILE NOT NULL NVARCHAR2(32) PKEY NOT NULL NVARCHAR2(50) VALUE NOT NULL NVARCHAR2(64) READONLY NOT NULL NUMBER(5) </pre> <p>This version without TO_NCHAR works fine in SQL Server and PostgreSQL (via ODBC) and SQLite (direct). However in Oracle it returns "ORA-12704: character set mismatch".</p> <pre><code>SQLPrepare(SELECT (CASE profile WHEN ? THEN 1 ELSE 2 END) AS profile_order FROM engine_properties;) = SQL_SUCCESS SQLBindParameter(hstmt, 1, SQL_PARAM_INPUT, SQL_C_WCHAR, SQL_VARCHAR, 32, 0, "_default", 18, 16) = SQL_SUCCESS SQLExecute() = SQL_ERROR SQLGetDiagRec(1) = SQL_SUCCESS [SQLSTATE: HY000, NATIVE: 12704, MESSAGE: [Oracle][ODBC] [Ora]ORA-12704: character set mismatch] SQLGetDiagRec(2) = SQL_NO_DATA </code></pre> <p>If I do use TO_NCHAR, it's okay (but won't work in SQL Server, Postgres, SQLite, etc).</p> <pre><code>SQLPrepare(SELECT (CASE profile WHEN TO_NCHAR(?) THEN 1 ELSE 2 END) AS profile_order FROM engine_properties;) = SQL_SUCCESS SQLBindParameter(hstmt, 1, SQL_PARAM_INPUT, SQL_C_WCHAR, SQL_VARCHAR, 32, 0, "_default", 18, 16) = SQL_SUCCESS SQLExecute() = SQL_SUCCESS SQLNumResultCols() = SQL_SUCCESS (count = 1) SQLFetch() = SQL_SUCCESS </code></pre>
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