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GBase 8s 提供了对 ROW 类型的支持，这使得在 JDBC 中处理嵌套数据结构变得更为灵活。
ROW 类型是一种复合数据类型，可以包含多个字段，每个字段都有自己的数据类型。在 GBase 8s 中，ROW 类型可以用于定义表的列、程序变量、语句变量以及例程返回值。通过 ROW 类型，可以更直观地表示和操作复杂的数据结构。
准备各个row类型：
CREATE ROW TYPE r1_t (i INT, b BOOLEAN);
CREATE ROW TYPE r2_t (f FLOAT, s MULTISET(INT8 NOT NULL), i INT);
CREATE ROW TYPE fullname_t (first CHAR(20), last CHAR(20));
CREATE ROW TYPE person_t (id INT, name fullname_t, age INT);
对应的几个SQLData实现类（只放核心代码）
public class r1_t implements SQLData {
int int_col;
boolean bool_col;
public String toString() {
String str = \"int_col: \" + int_col + \" bool_col: \" + bool_col;
return (str);
}
}
public class r2_t implements SQLData {
double dbl_col;
int int_col;
Collection mset_col;
public void readSQL(SQLInput stream, String typeName) throws SQLException {
dbl_col = stream.readDouble();
mset_col = (Collection) ((IfmxComplexSQLInput) stream).readObject();
int_col = stream.readInt();
}
public void writeSQL(SQLOutput stream) throws SQLException {
stream.writeDouble(dbl_col);
((IfmxComplexSQLOutput) stream).writeObject(mset_col);
stream.writeInt(int_col);
}
public String toString() {
String str = \"dbl_col: \" + dbl_col + \"n\";
str += \" int_col: \" + int_col + \"n\";
str += \" mset_col: n\";
Iterator it = mset_col.iterator();
Object element;
while (it.hasNext()) {
element = it.next();
str += \"tttelement: \" + element + \"n\";
}
return (str);
}
}
public class fullname implements SQLData {
public String first;
public String last;
}
public class person implements SQLData {
public int id;
public fullname name;
public int age;
public void readSQL(SQLInput stream, String type) throws SQLException {
sql_type = type;
id = stream.readInt();
name = (fullname) stream.readObject();
age = stream.readInt();
}
public void writeSQL(SQLOutput stream) throws SQLException {
stream.writeInt(id);
stream.writeObject(name);
stream.writeInt(age);
}
public String toString() {
String s = \"person:\";
s += \"id: \" + id + \"n\";
s += \" name: \" + name.toString() + \"n\";
s += \" age: \" + age + \"n\";
return s;
}
}
例1：
fetching a named row into a SQLData object
s = \"create table teachers (person person_t, dept char (20))\";
stmt.executeUpdate(s);
s = \"insert into teachers values (\'row(100, row(Bill, Smith), 27)\', \'physics\')\";
stmt.executeUpdate(s);
java.util.Map map = conn.getTypeMap();
map.put(\"fullname_t\", Class.forName(\"com.jdbc.demo.fullname\"));
map.put(\"person_t\", Class.forName(\"com.jdbc.demo.person\"));
pstmt = conn.prepareStatement(\"select person from teachers\");
rs = pstmt.executeQuery();
while (rs.next()) {
person who = (person) rs.getObject(1);
System.out.println(\"row: \" + who.toString());
}
输出：
row: person:id: 100
name: fullname: first: Bill last: Smith
age: 27
例2：
insert java object(SQLData) into a named row column
s = \"create table teachers (person person_t, dept char (20))\";
stmt.executeUpdate(s);
java.util.Map map = conn.getTypeMap();
map.put(\"fullname_t\", Class.forName(\"com.jdbc.demo.fullname\"));
map.put(\"person_t\", Class.forName(\"com.jdbc.demo.person\"));
person who = new person();
fullname name = new fullname();
name.last = \"Jones\";
name.first = \"Sarah\";
who.id = 567;
who.name = name;
who.age = 17;
String s = \"insert into teachers values (?, \'physics\')\";
pstmt = conn.prepareStatement(s);
pstmt.setObject(1, who);
int rowcount = pstmt.executeUpdate();
pstmt = conn.prepareStatement(\"select person::lvarchar from teachers\");
rs = pstmt.executeQuery();
while (rs.next()) {
String s = rs.getString(1);
System.out.println(\"lvarchar: \" + s);
}
输出：
lvarchar: ROW(567 ,ROW(\'Sarah \',\'Jones \'),17 )
例3：
fetch a unnamed SQLROW column into a Struct object
s = \"create table teachers (person row(id int, name row(first char(20), last char(20)), age int),dept char (20))\";
stmt.executeUpdate(s);
s = \"insert into teachers values (\'row(100, row(Bill, Smith), 27)\', \'physics\')\";
stmt.executeUpdate(s);
pstmt = conn.prepareStatement(\"select person from teachers\");
rs = pstmt.executeQuery();
rs.next();
Struct person = (Struct) rs.getObject(1);
String personRowType = person.getSQLTypeName();
System.out.println(\"person row description: \" + personRowType);
Integer id;
Struct name;
Integer age;
Object[] elements;
elements = person.getAttributes();
id = (Integer) elements[0];
name = (Struct) elements[1];
age = (Integer) elements[2];
System.out.println(\"person.id: \" + id);
System.out.println(\"person.age: \" + age);
String nameRowType = name.getSQLTypeName();
System.out.println(\"name row description: \" + nameRowType);
String first = (String) elements[0];
String last = (String) elements[1];
System.out.println(\"name.first: \" + first);
System.out.println(\"name.last: \" + last);
输出：
person row description: row ( id int , name row ( first char(20) , last char(20) ) , age int )
person.id: 100
person.age: 27
name row description: name row ( first char(20) , last char(20) ) // row前的name是列名
name.first: Bill
name.last: Smith
例4：
inserting a Struct object into a named row
public class GenericStruct implements java.sql.Struct {
private Object[] attributes = null;
private String typeName = null;
GenericStruct() {
}
GenericStruct(String name, Object[] obj) {
typeName = name;
attributes = obj;
}
public String getSQLTypeName() {
return typeName;
}
public Object[] getAttributes() {
return attributes;
}
public Object[] getAttributes(Map map) throws SQLException {
return attributes;
}
public void setAttributes(Object[] objArray) {
attributes = objArray;
}
public void setSQLTypeName(String name) {
typeName = name;
}
}
s = \"create table teachers (person person_t, dept char (20))\";
stmt.executeUpdate(s);
PreparedStatement pstmt;
ResultSet rs;
GenericStruct gs;
String rowType;
pstmt = conn.prepareStatement(\"insert into teachers values (?, \'Math\')\");
Object[] name = new Object[2];
name[0] = new String(\"Jane\");
name[1] = new String(\"Smith\");
rowType = \"row(first char(20), last char(20))\";
gs = new GenericStruct(rowType, name);
Object[] person = new Object[3];
person[0] = new Integer(99);
person[1] = gs;
person[2] = new Integer(56);
rowType = \"row(id int, name row(first char(20), last char(20)), age int)\";
gs = new GenericStruct(rowType, person);
pstmt.setObject(1, gs);
pstmt.executeUpdate();
pstmt.close();
pstmt = conn.prepareStatement(\"select person::lvarchar from teachers\");
rs = pstmt.executeQuery();
while (rs.next()) {
String s = rs.getString(1);
System.out.println(\"lvarchar: \" + s);
}
输出：
lvarchar: ROW(99 ,ROW(\'Jane \',\'Smith \'),56 )
例5：
Fetching and inserting a row(i int, b boolean) column
s = \"create table row_tab (int_col int, row_col r1_t)\";
stmt.executeUpdate(s);
s = \"insert into row_tab (int_col, row_col) values (?, ?)\";
pstmt = conn.prepareStatement(s);
java.util.Map customtypemap = conn.getTypeMap();
customtypemap.put(\"r1_t\", Class.forName(\"com.jdbc.demo.r1_t\"));
r1_t row = new r1_t(99, true);
pstmt.setInt(1, 1);
pstmt.setObject(2, row);
pstmt.executeUpdate();
// Select (i) -
// Fetch data using getObject() with customized type maping
s = \"select int_col, row_col from row_tab order by int_col\";
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(s);
rs.next();
int intret = rs.getInt(\"int_col\");
row = (r1_t) rs.getObject(\"row_col\");
System.out.println(row); // 输出：int_col: 99 bool_col: true
// ---------------------------------
// Selecting data as java.sql.Struct
// ---------------------------------
Vector objVector = new Vector();
String s = \"select int_col, row_col from row_tab order by int_col\";
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(s);
rs.next();
Struct row = (Struct) rs.getObject(\"row_col\", null);
Object[] objArray = row.getAttributes();
for (int i = 0; i < objArray.length; i++) {
System.out.println(\"ttfield: \" + objArray[i]);
}
输出：
field: 99
field: true
// -------------------------------------------------------
// Insert data using java.sql.Struct objects from previous select.
// -------------------------------------------------------
// 清空之前数据，略
s = \"insert into row_tab values (?, ?)\";
pstmt = conn.prepareStatement(s);
for (int i = 0; i < objVector.size(); i++) {
pstmt.setInt(1, i);
pstmt.setObject(2, objVector.get(i));
pstmt.executeUpdate();
}
String s = \"select int_col, row_col::lvarchar from row_tab order by int_col\";
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(s);
rs.next();
System.out.println(rs.getString(2)); // 输出：row_col ROW(99 ,\'t\')
例6：
s = \"create table row_tab (int_col int, row_col r2_t)\";
stmt.executeUpdate(s);
java.util.Map customtypemap = conn.getTypeMap();
customtypemap.put(\"r2_t\", Class.forName(\"r2_t\"));
String s = \"insert into row_tab (int_col, row_col) values (?, ?)\";
pstmt = conn.prepareStatement(s);
TreeSet set = new TreeSet();
set.add(new Long(1234567890));
set.add(new Long(-1234567890));
set.add(new Long(5));
row = new r2_t(1.67e30, set, 99);
pstmt.setInt(1, 1);
pstmt.setObject(2, row);
pstmt.executeUpdate();
String s = \"select int_col, row_col from row_tab order by int_col\";
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(s);
rs.next();
r2_t row = (r2_t) rs.getObject(\"row_col\");
System.out.println(row);
输出：
dbl_col: 1.67E30
int_col: 99
mset_col:
element: -1234567890
element: 5
element: 1234567890
例7：
s = \"create table row_tab (int_col int, row_col row(f float, l list(lvarchar not null), i int))\";
stmt.executeUpdate(s);
s = \"insert into row_tab (int_col, row_col) values (?, ?)\";
pstmt = conn.prepareStatement(s);
GenericStruct struct = null; // 同例4的GenericStruct
Object[] objArray = null;
ArrayList list = null;
list = new ArrayList();
list.add(new String(\"John Smith\"));
list.add(new String(\"Granny Apple\"));
list.add(new String(\"Barry White\"));
objArray = new Object[3];
objArray[0] = new Double(1.67e30);
objArray[1] = list;
objArray[2] = new Integer(99);
struct = new GenericStruct(rowDesc, objArray);
pstmt.setInt(1, 1);
pstmt.setObject(2, struct);
pstmt.executeUpdate();
s = \"select int_col, row_col from row_tab order by int_col\";
rs = stmt.executeQuery(s);
rs.next();
Struct row = (Struct) rs.getObject(\"row_col\");
System.out.println(\"Class: \" + row.getClass().getName());
System.out.println(\"SQLTypeName: \" + row.getSQLTypeName());
Object[] objArray = row.getAttributes();
for (int i = 0; i < objArray.length; i++) {
System.out.println(\"field: \" + objArray[i]);
}
输出：
Class: com.gbasedbt.jdbc.IfxStruct
SQLTypeName: row ( f float , l list ( lvarchar not null) , i int )
field: -1.67E30
field: [Roger Jones, Jeff Brown]
field: -99
本文通过一系列示例展示介绍了如何在 GBase 8s 的 JDBC 环境中使用 ROW 类型。如果你在实践中遇到任何问题，欢迎随时在社区中提问，我们在这里为你提供支持！
原文链接：www.gbase.cn/community/p…
更多精彩内容尽在南大通用GBase技术社区，南大通用致力于成为用户最信赖的数据库产品供应商。
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