--获取当前月份的第一天
SELECT TRUNC (SYSDATE, 'MONTH') "First day of current month"
FROM DUAL;
--获取当前月份的最后一天
SELECT TRUNC (LAST_DAY (SYSDATE)) "Last day of current month"
FROM DUAL;
--获取当前年份的第一天
SELECT TRUNC (SYSDATE, 'YEAR') "Year First Day" FROM DUAL;
--获取当前年份的最后一天
SELECT ADD_MONTHS (TRUNC (SYSDATE, 'YEAR'), 12) - 1 "Year Last Day" FROM DUAL;
--获取当前月份的天数
SELECT CAST (TO_CHAR (LAST_DAY (SYSDATE), 'dd') AS INT) number_of_days FROM DUAL;
--获取当前月份剩下的天数
SELECT SYSDATE,
LAST_DAY (SYSDATE) "Last",
LAST_DAY (SYSDATE) - SYSDATE "Days left"
FROM DUAL;
--获取两个日期之间的天数
SELECT ROUND ((MONTHS_BETWEEN ('01-Feb-2014', '01-Mar-2012') * 30), 0) num_of_days FROM DUAL;
OR
SELECT TRUNC(sysdate) - TRUNC(e.hire_date) FROM employees;
--显示当前年份截止到本月每个月份开始和结束的日期
SELECT ADD_MONTHS (TRUNC (SYSDATE, 'MONTH'), i) start_date,
TRUNC (LAST_DAY (ADD_MONTHS (SYSDATE, i))) end_date
FROM XMLTABLE (
'for $i in 0 to xs:int(D) return $i'
PASSING XMLELEMENT (
d,
FLOOR (
MONTHS_BETWEEN (
ADD_MONTHS (TRUNC (SYSDATE, 'YEAR') - 1, 12),
SYSDATE)))
COLUMNS i INTEGER PATH '.');
--把数值转换成文字
SELECT TO_CHAR (TO_DATE (1526, 'j'), 'jsp') FROM DUAL;
--获取拥有者的对象数量
SELECT owner, COUNT (owner) number_of_objects
FROM dba_objects
GROUP BY owner
ORDER BY number_of_objects DESC;
--查询并显示连接 Oracle 的用户和用户的会话数量
SELECT username Usuario_Oracle, COUNT (username) Numero_Sesiones
FROM v$session
GROUP BY username
ORDER BY Numero_Sesiones DESC;
--查询并显示通过打开连接程序打开连接的组
SELECT program application, COUNT (program) Numero_Sesiones
FROM v$session
GROUP BY program
ORDER BY Numero_Sesiones DESC;
--在视图中查询并显示实际的 Oracle 连接
SELECT osuser,
username,
machine,
program
FROM v$session
ORDER BY osuser;
--查询每个执行读取的前十个 SQL
SELECT *
FROM ( SELECT ROWNUM,
SUBSTR (a.sql_text, 1, 200) sql_text,
TRUNC (
a.disk_reads / DECODE (a.executions, 0, 1, a.executions))
reads_per_execution,
a.buffer_gets,
a.disk_reads,
a.executions,
a.sorts,
a.address
FROM v$sqlarea a
ORDER BY 3 DESC)
WHERE ROWNUM < 10;
--查询特定的模式或者表中执行的最后一个 SQL 语句
SELECT CREATED, TIMESTAMP, last_ddl_time
FROM all_objects
WHERE OWNER = 'MYSCHEMA'
AND OBJECT_TYPE = 'TABLE'
AND OBJECT_NAME = 'EMPLOYEE_TABLE';
--获取当前会话 ID，进程 ID，客户端 ID 等
SELECT b.sid,
b.serial#,
a.spid processid,
b.process clientpid
FROM v$process a, v$session b
WHERE a.addr = b.paddr AND b.audsid = USERENV ('sessionid');
--查询数据库长查询进展情况
SELECT a.sid,
a.serial#,
b.username,
opname OPERATION,
target OBJECT,
TRUNC (elapsed_seconds, 5) "ET (s)",
TO_CHAR (start_time, 'HH24:MI:SS') start_time,
ROUND ( (sofar / totalwork) * 100, 2) "COMPLETE (%)"
FROM v$session_longops a, v$session b
WHERE a.sid = b.sid
AND b.username NOT IN ('SYS', 'SYSTEM')
AND totalwork > 0
ORDER BY elapsed_seconds;
--查询用户 CPU 的使用率
SELECT ss.username, se.SID, VALUE / 100 cpu_usage_seconds
FROM v$session ss, v$sesstat se, v$statname sn
WHERE se.STATISTIC# = sn.STATISTIC#
AND NAME LIKE '%CPU used by this session%'
AND se.SID = ss.SID
AND ss.status = 'ACTIVE'
AND ss.username IS NOT NULL
ORDER BY VALUE DESC;
--查询数据库中每个用户最后使用的 SQL 查询
SELECT S.USERNAME || '(' || s.sid || ')-' || s.osuser UNAME,
s.program || '-' || s.terminal || '(' || s.machine || ')' PROG,
s.sid || '/' || s.serial# sid,
s.status "Status",
p.spid,
sql_text sqltext
FROM v$sqltext_with_newlines t, V$SESSION s, v$process p
WHERE t.address = s.sql_address
AND p.addr = s.paddr(+)
AND t.hash_value = s.sql_hash_value
ORDER BY s.sid, t.piece;
--查询模式或者用户的大小
SELECT SUM (bytes / 1024 / 1024) "size"
FROM dba_segments
WHERE owner = '&owner';
--查询数据库中数据占用的大小或者是数据库使用细节
SELECT SUM (bytes) / 1024 / 1024 / 1024 AS GB FROM dba_segments;
--查询数据库的实际大小
SELECT SUM (bytes) / 1024 / 1024 / 1024 AS GB FROM dba_data_files;
--增加数据文件的大小
ALTER DATABASE DATAFILE '/u01/app/Test_data_01.dbf' RESIZE 2G;
--在表空间添加数据文件
ALTER TABLESPACE data01 ADD DATAFILE '/work/oradata/STARTST/data01.dbf'
SIZE 1000M AUTOEXTEND OFF;
--检查表空间的自动扩展开关
SELECT SUBSTR (file_name, 1, 50), AUTOEXTENSIBLE FROM dba_data_files;
(OR)
SELECT tablespace_name, AUTOEXTENSIBLE FROM dba_data_files;
--调整没有添加数据文件的表空间
ALTER DATABASE DATAFILE '/work/oradata/STARTST/STAR02D.dbf' resize 2000M;
--存储区分大小写的数据，但是索引不区分大小写
CREATE TABLE tab (col1 VARCHAR2 (10));
CREATE INDEX idx1
ON tab (UPPER (col1));
ANALYZE TABLE a COMPUTE STATISTICS;
--获取 Oracle 版本
SELECT VALUE
FROM v$system_parameter
WHERE name = 'compatible';
--数据库字符设置信息
SELECT * FROM nls_database_parameters;
--数据库默认信息
SELECT username,
profile,
default_tablespace,
temporary_tablespace
FROM dba_users;
--数据库版本信息
SELECT * FROM v$version;
--修改当前模式
ALTER SESSION SET CURRENT_SCHEMA = new_schema;
--获取当前模式
SELECT SYS_CONTEXT ('userenv', 'current_schema') FROM DUAL;
--显示表结构
SELECT DBMS_METADATA.get_ddl ('TABLE', 'TABLE_NAME', 'USER_NAME') FROM DUAL;
--检查在当前表中是否存在指定的列
SELECT column_name AS FOUND
FROM user_tab_cols
WHERE table_name = 'TABLE_NAME' AND column_name = 'COLUMN_NAME';
--检查在当前数据库模式下是否存在指定的表
SELECT table_name
FROM user_tables
WHERE table_name = 'TABLE_NAME';
--获取今天剩下的秒数（直到 23：59：59 结束）
SELECT (TRUNC (SYSDATE+1) - SYSDATE) * 24 * 60 * 60 num_of_sec_left FROM DUAL;
--获取直到目前为止今天过去的秒数（从 00：00 开始算）
SELECT (SYSDATE - TRUNC (SYSDATE)) * 24 * 60 * 60 num_of_sec_since_morning FROM DUAL;
--在包的源代码中查询字符串 search a string foo_something in package source code
SELECT *
FROM dba_source
WHERE UPPER (text) LIKE '%FOO_SOMETHING%'
AND owner = 'USER_NAME';
--把用逗号分隔的数据插入的表中
WITH csv
AS (SELECT 'AA,BB,CC,DD,EE,FF'
AS csvdata
FROM DUAL)
SELECT REGEXP_SUBSTR (csv.csvdata, '[^,]+', 1, LEVEL) pivot_char
FROM DUAL, csv
CONNECT BY REGEXP_SUBSTR (csv.csvdata,'[^,]+', 1, LEVEL) IS NOT NULL;
--查询表中的最后一个记录
SELECT *
FROM employees
WHERE ROWID IN (SELECT MAX (ROWID) FROM employees);
(OR)
SELECT * FROM employees
MINUS
SELECT *
FROM employees
WHERE ROWNUM < (SELECT COUNT (*) FROM employees);
--在 Oracle 中做行数据乘法
WITH tbl
AS (SELECT -2 num FROM DUAL
UNION
SELECT -3 num FROM DUAL
UNION
SELECT -4 num FROM DUAL),
sign_val
AS (SELECT CASE MOD (COUNT (*), 2) WHEN 0 THEN 1 ELSE -1 END val
FROM tbl
WHERE num < 0)
SELECT EXP (SUM (LN (ABS (num)))) * val
FROM tbl, sign_val
GROUP BY val;
--在 Oracle 中生成随机数值 generate random number between 0 and 100
SELECT ROUND (DBMS_RANDOM.VALUE () * 100) + 1 AS random_num FROM DUAL;
--在 Oracle 生成随机数据
SELECT LEVEL empl_id,
MOD (ROWNUM, 50000) dept_id,
TRUNC (DBMS_RANDOM.VALUE (1000, 500000), 2) salary,
DECODE (ROUND (DBMS_RANDOM.VALUE (1, 2)), 1, 'M', 2, 'F') gender,
TO_DATE (
ROUND (DBMS_RANDOM.VALUE (1, 28))
|| '-'
|| ROUND (DBMS_RANDOM.VALUE (1, 12))
|| '-'
|| ROUND (DBMS_RANDOM.VALUE (1900, 2010)),
'DD-MM-YYYY')
dob,
DBMS_RANDOM.STRING ('x', DBMS_RANDOM.VALUE (20, 50)) address
FROM DUAL
CONNECT BY LEVEL < 10000;
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