package cn.org.rapid_framework.jdbc.dialect;
/**
*
* @author badqiu
*
*/
// Hibernate BUG: http://opensource.atlassian.com/projects/hibernate/browse/HHH-2655
// TODO 完善并测试SQLServer2005Dialect
public class SQLServer2005Dialect extends Dialect{
@Override
public boolean supportsLimit() {
return true;
}
@Override
public boolean supportsLimitOffset() {
return true;
}
/**
* Add a LIMIT clause to the given SQL SELECT
*
* The LIMIT SQL will look like:
*
* WITH query AS
* (SELECT TOP 100 percent ROW_NUMBER() OVER (ORDER BY CURRENT_TIMESTAMP) as __row_number__, * from table_name)
* SELECT *
* FROM query
* WHERE __row_number__ BETWEEN :offset and :lastRows
* ORDER BY __row_number__
*
* @param querySqlString The SQL statement to base the limit query off of.
* @param offset Offset of the first row to be returned by the query (zero-based)
* @param last Maximum number of rows to be returned by the query
* @return A new SQL statement with the LIMIT clause applied.
*/
@Override
public String getLimitString(String querySqlString, int offset,String offsetPlaceholder, int limit, String limitPlaceholder) {
StringBuffer pagingBuilder = new StringBuffer();
String orderby = getOrderByPart(querySqlString);
String distinctStr = "";
String loweredString = querySqlString.toLowerCase();
String sqlPartString = querySqlString;
if (loweredString.trim().startsWith("select")) {
int index = 6;
if (loweredString.startsWith("select distinct")) {
distinctStr = "DISTINCT ";
index = 15;
}
sqlPartString = sqlPartString.substring(index);
}
pagingBuilder.append(sqlPartString);
// if no ORDER BY is specified use fake ORDER BY field to avoid errors
if (orderby == null || orderby.length() == 0) {
orderby = "ORDER BY CURRENT_TIMESTAMP";
}
StringBuffer result = new StringBuffer();
result.append("WITH query AS (SELECT ")
.append(distinctStr)
.append("TOP 100 PERCENT ")
.append(" ROW_NUMBER() OVER (")
.append(orderby)
.append(") as __row_number__, ")
.append(pagingBuilder)
.append(") SELECT * FROM query WHERE __row_number__ BETWEEN ")
.append(offset).append(" AND ").append(offset+limit)
.append(" ORDER BY __row_number__");
return result.toString();
}
static String getOrderByPart(String sql) {
String loweredString = sql.toLowerCase();
int orderByIndex = loweredString.indexOf("order by");
if (orderByIndex != -1) {
// if we find a new "order by" then we need to ignore
// the previous one since it was probably used for a subquery
return sql.substring(orderByIndex);
} else {
return "";
}
}
}