时间：2021-07-01 10:21:17 帮助过：23人阅读
-- Create table
create table TEMP
(
name VARCHAR2(200),
age NUMBER,
temp_clob CLOB
)
tablespace INSIGHTDATA3_TS
pctfree 10
initrans 1
maxtrans 255
storage
(
initial 160K
next 1M
minextents 1
maxextents unlimited
);
SELECT t.name, t.temp_clob FROM temp t; --普通查询 INSERT INTO temp t VALUES (‘Grand.Jon‘, 22, ‘加入博客园的第一天‘);
查询因为不是varchar2类型，所以普通查询看不到CLOB类型的字段内容，结果如下
而普通插入操作也会因为Oracle的隐式转换，默认把字符串转换成varchar2类型，一旦字符串内容超过varchar2的最大限度就会报会报ora-01704（字符串太长）错误。
--使用PL/SQL语法，采取绑定变量的方式解决，而不是直接拼接SQL
DECLARE
V_LANG CLOB := ‘待插入的海量字符串‘;
V_UPDATE CLOB := ‘更新的海量字符串‘;
BEGIN
INSERT INTO temp t VALUES (‘Grand.Jon‘, 22, V_LANG); --增加
UPDATE temp t SET t.temp_clob = V_UPDATE WHERE rownum = 1; --修改
SELECT t.NAME, dbms_lob.substr(t.temp_clob) FROM TEMP t; --查询 将CLOB转成字符类型
DELETE temp t WHERE rownum = 1; --按列删除
COMMIT;
END;
/
对CLOB的操作我们在存储过程中基本上使用 dbms_lob 中 substr , append , write 等方法。
1 dbms_lob.createtemporary(V_SQL,true); --创建一个临时clob，用来存储拼接的sql 2 dbms_lob.write(v_SQL,‘写入信息‘); --写入操作 3 dbms_lob.append(v_SQL,‘,‘); --拼接clob 4 dbms_lob.substr(v_SQL); --截取clob，不传参数就是全部读取 5 dbms_lob.freetemporary(v_SQL); --释放clob
查询结果如下：
需求：以开发的存储过程为例，需要循环遍历时间范围拼接sql，将时间日期按列反转（pivot），如果时间太长（1年以上）sql语句（varchar2）就会超出范围报错，这时候就需要使用CLOB来存储拼接的sql。
PROCEDURE P_AND_CPT_RATIOOTH_APP_BAK2_N(
V_APPIDS IN VARCHAR2,
V_TYPE IN VARCHAR2,
V_CHANNEL IN VARCHAR2,
V_TABLE IN VARCHAR2,
V_START IN VARCHAR2,
V_END IN VARCHAR2,
RESULT OUT mycursor
) IS
V_SQL CLOB;
V_SQLWHERE VARCHAR2(32767) default ‘‘;
V_SQLWHERE_CHANNEL VARCHAR2(32767) default ‘‘;
V_SQL_DATES CLOB;
V_Sdate DATE;
V_Edate DATE;
V_TABLE_DATE VARCHAR2(50);
V_TABLE_TYPE VARCHAR2(50);
V_START_DATE VARCHAR2(50);
V_END_DATE VARCHAR2(50);
V_DAY VARCHAR2(50);
BEGIN
select column_name into V_TABLE_DATE from user_tab_columns where table_name=‘‘||V_TABLE||‘‘ and column_id=1;
select column_name into V_TABLE_TYPE from user_tab_columns where table_name=‘‘||V_TABLE||‘‘ and column_id=5;
dbms_lob.createtemporary(V_SQL,true);--创建一个临时lob
dbms_lob.createtemporary(V_SQL_DATES,true);--创建一个临时lob
IF V_APPIDS is NOT NULL THEN
V_SQLWHERE := ‘AND t.appid in (‘||V_APPIDS||‘)‘;
END IF;
IF V_CHANNEL IS NOT NULL THEN
V_SQLWHERE_CHANNEL := ‘AND t.channel = ‘‘‘||V_CHANNEL||‘‘‘‘;
END IF;
IF V_TABLE_DATE = ‘MON‘ THEN
V_START_DATE := SUBSTR(V_START,0,6);
V_END_DATE := SUBSTR(V_END,0,6);
v_sdate := to_date(V_START_DATE, ‘yyyymm‘);
v_edate := to_date(V_END_DATE, ‘yyyymm‘);
WHILE (v_sdate <= v_edate) LOOP
dbms_lob.append(v_SQL_DATES,to_char(v_sdate, ‘yyyymm‘));--把临时字符串付给v_str
IF v_sdate != v_edate THEN
dbms_lob.append(v_SQL_DATES,‘,‘);--把临时字符串付给v_str
END IF;
v_sdate := add_months(v_sdate,1);
END LOOP;
ELSE --周和日 类型 都是 DAY
v_sdate := to_date(V_START, ‘yyyymmdd‘);
v_edate := to_date(V_END, ‘yyyymmdd‘);
V_END_DATE := V_END;
IF SUBSTR(V_TYPE,0,1)=‘d‘ THEN
V_START_DATE := to_char(v_sdate, ‘yyyymmdd‘);
WHILE (v_sdate <= v_edate) LOOP
dbms_lob.append(v_SQL_DATES,to_char(v_sdate, ‘yyyymmdd‘));--把临时字符串付给v_str
IF v_sdate != v_edate THEN
dbms_lob.append(v_SQL_DATES,‘,‘);--把临时字符串付给v_str
END IF;
v_sdate := v_sdate+1;
END LOOP;
ELSIF SUBSTR(V_TYPE,0,1)=‘w‘ THEN
select to_char(V_Sdate,‘d‘) INTO V_DAY from dual;
IF V_DAY!=2 THEN
V_Sdate:=V_Sdate-7;
END IF;
V_START_DATE := to_char(v_sdate, ‘yyyymmdd‘);
WHILE (v_sdate <= v_edate) LOOP
select to_char(V_Sdate,‘d‘) INTO V_DAY from dual;
IF V_DAY=2 THEN
dbms_lob.append(v_SQL_DATES,to_char(v_sdate, ‘yyyymmdd‘));--把临时字符串付给v_str
IF V_Edate-v_sdate >7 THEN
dbms_lob.append(v_SQL_DATES,‘,‘);--把临时字符串付给v_str
END IF;
END IF;
v_sdate := v_sdate+1;
END LOOP;
END IF;
END IF;
dbms_lob.append(v_sql,‘SELECT * FROM( SELECT *
FROM ‘||V_TABLE||‘ t
WHERE
t.‘||V_TABLE_TYPE||‘ = ‘‘‘||V_TYPE||‘‘‘
AND t.‘||V_TABLE_DATE||‘ >= ‘‘‘||V_START_DATE||‘‘‘
AND t.‘||V_TABLE_DATE||‘ <= ‘‘‘||V_END_DATE||‘‘‘
‘||V_SQLWHERE||‘
‘||V_SQLWHERE_CHANNEL||‘ ) t1
pivot(sum(MARKETSHARE)
for ‘||V_TABLE_DATE||‘ in(‘);
dbms_lob.append(v_sql,v_SQL_DATES);
dbms_lob.append(v_sql,‘))‘);
dbms_output.put_line(v_sql);
OPEN result FOR v_sql;
dbms_lob.freetemporary(v_sql);--释放lob
dbms_lob.freetemporary(v_SQL_DATES);--释放lob
--dbms_output.put_line(V_SQLDATE);
-- dbms_output.put_line(v_SQL_DATES);
--记录操作日志及错误日志
END;
重点：这两步操作要放在同一个事务里面。具体增加的方法如下:
public boolean save(Article article){
boolean result = true;
Connection conn = ConnectionUntils.getInstance();
String sql = "insert into temp values(?,?,empty_clob())";
//锁住该列，防止并发写入时候该字段同时被多次写入造成错误
String sqlClob = "select temp_clob from temp t where t.name=? for update";
PreparedStatement pst =null;
ResultSet rs = null;
Writer writer = null;
try {
conn.setAutoCommit(false);//设置不自动提交，开启事务
pst = conn.prepareStatement(sql);
pst.setString(1,article.getName());
pst.setString(2,article.getAge());
pst.executeUpdate();
pst= conn.prepareStatement(sqlClob);
pst.setInt(1, article.getId());
rs = pst.executeQuery();
CLOB clob = null;
if(rs.next()){
try {
clob = (CLOB) rs.getClob(1);
writer = clob.getCharacterOutputStream(); //拿到clob的字符输入流
writer.write(article.getContent());
writer.flush();
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
}
conn.commit();
} catch (SQLException e) {
result = false;
try {
conn.rollback();//当commit或者rollback后会自动释放该列的锁定
} catch (SQLException e1) {
e1.printStackTrace();
}
e.printStackTrace();
} finally {
conn.setAutoCommit(true);//还原
ConnectionUntils.close(rs, pst, conn);
}
return result;
}
public boolean update(String name,String content){
int result = 0;
Connection conn = ConnectionUntils.getInstance();
String sql = "update temp set temp_clob=? where name=?";
PreparedStatement pst =null;
try {
CLOB clob = oracle.sql.CLOB.createTemporary(conn, false,oracle.sql.CLOB.DURATION_SESSION);
clob.setString(1L, content);
pst = conn.prepareStatement(sql);
pst.setClob(1, clob);
pst.setString(2,name);
result = pst.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}finally{
ConnectionUntils.close(null, pst, conn);
}
if(result==0)
return false;
return true;
}
public Article select(String name){
Article article = new Article();
Connection conn = ConnectionUntils.getInstance();
String sql = "select name,age,temp_clog from temp where name = ?";
PreparedStatement pst =null;
ResultSet rs = null;
try {
pst = conn.prepareStatement(sql);
pst.setInt(1,id);
rs = pst.executeQuery();
StringBuilder builder = new StringBuilder();
if(rs.next()){
Clob clob = rs.getClob("temp_clog");
Reader rd = clob.getCharacterStream();
char [] str = new char[12];
while(rd.read(str) != -1) {
builder.append(new String(str));
}
article.setContent(builder.toString());
article.setName(rs.getString("name"));
article.setAge(rs.getInt("age"));
}
} catch (SQLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}finally{
ConnectionUntils.close(rs, pst, conn);
}
return article;
}
譬如：Mybatis
<result column="temp_clob" property="content" jdbcType="Clob" typeHandler="org.apache.ibatis.type.ClobTypeHandler"/>
貌似Hibernate5内部做了对应的处理，可以直接当string类型一样处理即可。
虽然CLOB能解决VARCHAR2字符大小的限制，但是我们的DBA们都不建议用这些来处理，可能效率问题吧，大的文件应该放在服务器上，然后Database中存响应地址即可。
if ( U.read(me.Blog) ) $("#推荐").click();
if ( U.copy(me.Blog) ) $("#u Blog").console("原文链接：http://www.cnblogs.com/Grand-Jon/p/7389427.html ");
else me.Fuck(U);
Oracle的CLOB大数据字段类型（转）
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