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package org.nbone.persistence.jdbc.dialect;
/**
 * 类似hibernate的Dialect,但只精简出分页部分  模仿hibernate的JDBC方言，用于jdbc的分页
 * @author thinking
 */
public abstract class Dialect {
	
    public boolean supportsLimit(){
    	return false;
    }

    public boolean supportsLimitOffset() {
    	return supportsLimit();
    }
    
    /**
     * 将sql变成分页sql语句,直接使用offset,limit的值作为占位符.

     * 源代码为: getLimitString(sql,offset,String.valueOf(offset),limit,String.valueOf(limit))
     */
    public String getLimitString(String sql, int offset, int limit) {
    	return getLimitString(sql,offset,Integer.toString(offset),limit,Integer.toString(limit));
    }
    
    /**
     * 将sql变成分页sql语句,提供将offset及limit使用占位符(placeholder)替换.
     *      * 如mysql
     * dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
     * select * from user limit :offset,:limit
     * 
     * @return 包含占位符的分页sql
     */
    public String getLimitString(String sql, int offset,String offsetPlaceholder, int limit,String limitPlaceholder) {
    	throw new UnsupportedOperationException("paged queries not supported");
    }
    
}