Firebird/InterBase内置函数使用说明(转自：圣域天堂) 2008-10-12 20:56 加*号为FB2.0加入的函数 整理:剑雷(jianlei) 2006-10-13
1. COUNT, AVG, MAX, MIN, SUM 说明:通用统计函数,不详细介绍了
2. EXTRACT(timestamp_part FROM value) 说明:EXTRACT(YEAR/MONTHE/DAY/WEEKDAY FROM 字段名) 从日期型字段中分离出年,月,日及一个星期的第几天
3. CAST(value AS datatype) 说明:转换数据类型
4. LOWER() * 说明:返回小写值
5. UPPER() 说明:返回大写值
6. TRIM() * 说明:去除字符串两边的空格
7. SUBSTRING(string FROM pos FOR length) 说明:取字符串子串,注意,第一个字符的位置是1
8. BIT_LENGTH * 说明:返回字符串位(bit)数
9. CHAR_LENGTH/CHARACTER_LENGTH * 说明:返回字符串字符数
10. OCTET_LENGTH * 说明:返回字符串字节数
11. CASE 说明:通过执行外来的一组条件取得相应的返回值 举例 i) 简单 SELECT o.ID, o.Description, CASE o.Status WHEN 1 THEN 'confirmed' WHEN 2 THEN 'in production' WHEN 3 THEN 'ready' WHEN 4 THEN 'shipped' ELSE 'unknown status ''' || o.Status || '''' END FROM Orders o; ii) 表达式 SELECT o.ID, o.Description, CASE WHEN (o.Status IS NULL) THEN 'new' WHEN (o.Status = 1) THEN 'confirmed' WHEN (o.Status = 3) THEN 'in production' WHEN (o.Status = 4) THEN 'ready' WHEN (o.Status = 5) THEN 'shipped' ELSE 'unknown status ''' || o.Status || '''' END FROM Orders o;
12. IIF (<search_condition>, <value1>, <value2>) 说明:表达式为真,返回value1否则返回value2 等价于以下语句: CASE WHEN <search_condition> THEN <value1> ELSE <value2> END
13. NULLIF(V1,V2) 说明:如果V1=V2,返回NULL,否则返回V1 等价于以下语句: CASE WHEN V1 = V2 THEN NULL ELSE V1 END 举例 UPDATE PRODUCTS SET STOCK = NULLIF(STOCK,0)
14. COALESCE(V1, V2, …, Vn) 说明:如果V1为Null,返回V2,否则返回V1, 如果 n >= 3, 等于如下case语句: CASE WHEN V1 IS NOT NULL THEN V1 ELSE COALESCE (V2,...,Vn) END
举例 SELECT PROJ_NAME AS Projectname, COALESCE(e.FULL_NAME,'[< not assigned >]') AS Employeename FROM PROJECT p LEFT JOIN EMPLOYEE e ON (e.EMP_NO = p.TEAM_LEADER);
SELECT COALESCE(Phone,MobilePhone,'Unknown') AS "Phonenumber" FROM Relations; 15.获当前日期： select current_date from rdb$database 获当前时间： select current_time from rdb$database
16.Firebird数据库的取值范围 在其它SQL数据库里，有一个 Top n的子句，可以取头n条记录，Firebird不支持这个子句，但是它有更强大的子句：FIREST n SKIP n。 FIRST n表示提取头n条记录,SKIP n 表示从第几条开始提取，比如，我要从学生表里取语文成绩名次在11至15名的学生名单，SQL语句如下： select first 5 skip 10 SNAME,YUWEN from achieve order by YUWEN desc
一、分页写法小例： SELECT FIRST 10 templateid,code,name FROM template ; SELECT FIRST 10 SKIP 10 templateid,code,name FROM template ; SELECT * FROM shop ROWS 1 TO 10; --firebird2.0支持这种写法
二、显示表名和表结构 SHOW TABLES; SHOW TABLE tablename;
三、使用ISQL连接数据库 firebird%92bin>isql -u sysdba -p masterkey SQL>CONNECT 'E:companyxmwsoftnewxmwsoftc2dbcts2.fdb'; 或 SQL>CONNECT 'E:%92' CON>USER 'sysdba' CONT>PASSWORD 'masterkey';
四、更新字段注释 UPDATE RDB$RELATION_FIELDS SET RDB$DESCRIPTION = '描述信息' WHERE (RDB$RELATION_NAME = 'SHOP') AND (RDB$FIELD_NAME = 'CREDIT_BUY')
五、显示字段注释 SELECT RDB$FIELD_NAME,RDB$DESCRIPTION FROM RDB$RELATION_FIELDS WHERE (RDB$RELATION_NAME = 'SHOP') AND (DB$FIELD_NAME = 'CREDIT_BUY')
六、更新表注释 UPDATE RDB$RELATIONS SET RDB$DESCRIPTION = '描述信息' WHERE RDB$RELATION_NAME = 'TABLE_NAME';
七、查询所有的表和视图（包括系统表和系统视图） SELECT RDB$RELATION_NAME FROM RDB$RELATIONS;
八、查询所有的用户表和用户视图 SELECT RDB$RELATION_NAME FROM RDB$RELATIONS WHERE RDB$SYSTEM_FLAG = 0;
九、查询所有的用户表 SELECT RDB$RELATION_NAME FROM RDB$RELATIONS WHERE RDB$SYSTEM_FLAG = 0 AND RDB$VIEW_BLR IS NULL;
十、查所有用户表、用户视图所有字段及相关定义 SELECT a.RDB$RELATION_NAME, b.RDB$FIELD_NAME, b.RDB$FIELD_ID, d.RDB$TYPE_NAME, c.RDB$FIELD_LENGTH, c.RDB$FIELD_SCALE FROM RDB$RELATIONS a INNER JOIN RDB$RELATION_FIELDS b ON a.RDB$RELATION_NAME = b.RDB$RELATION_NAME INNER JOIN RDB$FIELDS c ON b.RDB$FIELD_SOURCE = c.RDB$FIELD_NAME INNER JOIN RDB$TYPES d ON c.RDB$FIELD_TYPE = d.RDB$TYPE WHERE a.RDB$SYSTEM_FLAG = 0 AND d.RDB$FIELD_NAME = 'RDB$FIELD_TYPE' ORDER BY a.RDB$RELATION_NAME, b.RDB$FIELD_ID;
十一、查找某表的所有字段及相关定义 SELECT A.RDB$FIELD_NAME, B.RDB$FIELD_TYPE, B.RDB$FIELD_LENGTH, B.RDB$FIELD_PRECISION, B.RDB$FIELD_SCALE FROM RDB$RELATION_FIELDS A, RDB$FIELDS B WHERE A.RDB$RELATION_NAME = 'tablename' AND A.RDB$FIELD_SOURCE = B.RDB$FIELD_NAME ORDER BY A.RDB$FIELD_POSITION;
十二、查找某表的主键定义字段 SELECT A.RDB$FIELD_NAME FROM RDB$INDEX_SEGMENTS A, RDB$RELATION_CONSTRAINTS B WHERE B.RDB$CONSTRAINT_TYPE = 'PRIMARY KEY' AND B.RDB$RELATION_NAME = 'tablename' AND A.RDB$INDEX_NAME = B.RDB$INDEX_NAME ORDER BY A.RDB$FIELD_POSITION;
十三、查找某表的外键定义 SELECT r1.RDB$CONSTRAINT_NAME, rind.RDB$FIELD_NAME, r2.RDB$RELATION_NAME FROM RDB$RELATION_CONSTRAINTS r1, RDB$RELATION_CONSTRAINTS r2, RDB$REF_CONSTRAINTS ref, RDB$INDEX_SEGMENTS rind WHERE r1.RDB$RELATION_NAME = 'tablename' AND r1.RDB$CONSTRAINT_TYPE = 'FOREIGN KEY' AND r1.RDB$CONSTRAINT_NAME = ref.RDB$CONSTRAINT_NAME AND ref.RDB$CONST_NAME_UQ = r2.RDB$CONSTRAINT_NAME AND r1.RDB$INDEX_NAME = rind.RDB$INDEX_NAME;