# 一、元数据
## 1.1 存储过程
+ 查看所有存储过程
```sql
select distinct name From user_source where type = 'PROCEDURE'
```
+ 查看存储过程语句
```sql
SELECT text
    FROM user_source
   WHERE NAME = 'EXECUTE_JOB_FINANCE_SURVEY'
ORDER BY line
```
## 1.2 表
+ 查看所有表
```sql
# 查询当前用户
select * from user_tab_comments where table_type='TABLE';
# 查询所有用户,当前用户必须有sysdba权限
select * from all_tab_comments
```
+ 查看表所有字段
```sql
SELECT
	COLUMN_NAME,
	DATA_TYPE 
FROM
	user_tab_columns 
WHERE
	table_name = 'DW_INFRASTRUCTURE_SURVEY' 
ORDER BY
	COLUMN_ID ASC;
```
+ 查看具体字段
```sql
SELECT
	COLUMN_NAME,
	DATA_TYPE,
	DATA_LENGTH,
	NULLABLE,
	DEFAULT_LENGTH,
	DATA_DEFAULT 
FROM
	user_tab_columns 
WHERE
	table_name = 'DW_INFRASTRUCTURE_SURVEY' 
	AND COLUMN_NAME = 'STATISTICAL_TIME' 
ORDER BY
	COLUMN_ID ASC;
```
+ 查看字段及注释
```sql
SELECT
	b.COLUMN_NAME,
	a.COMMENTS,
	case when DATA_PRECISION is null and DATA_SCALE=0 and DATA_TYPE='NUMBER' then 'NUMBER(38,0)' when 
	DATA_PRECISION is not null and DATA_SCALE>0 then 'NUMBER('||DATA_PRECISION||','||DATA_SCALE||')' when
	DATA_TYPE<>'DATE' then DATA_TYPE||'('||DATA_LENGTH||')'  else DATA_TYPE end as  DATA_TYPE_,
	b.NULLABLE,
	b.DATA_LENGTH,
	b.DEFAULT_LENGTH,
	b.DATA_DEFAULT,
	DATA_PRECISION,
	DATA_SCALE,
	b.COLUMN_ID,
	b.DATA_TYPE
FROM
	user_col_comments a
	LEFT JOIN user_tab_columns b ON a.table_name = b.table_name 
	AND a.COLUMN_NAME = b.COLUMN_NAME 
WHERE
	a.table_name = 'OA_VEHICLE_OIL_CHARGE' 
ORDER BY
	b.COLUMN_ID ASC
```

+ 修改表备注
```
# 表备注
Comment on table DW_RE_PROGRESS_DETAIL is '项目进度-进度明细';
# 字段备注
comment on column Student.id is '学生id';  
comment on column Student.name is '学生姓名';
```

## 1.3 视图
+ 查询当前用户所有视图
```sql
select * from user_tab_comments where table_type='VIEW'
```

+ 视图创建语句
```sql
select text from all_views where view_name='DW_SAFETY_RISK_LARG_QS_VW'
```

# 二、常用函数
## 2.1 行转列、列转行
+ pivot
```sql
--行转列
select *
  from SalesList pivot(
    max(salesNum) for shangPin in (    --shangPin 即要转成列的字段
        '上衣' as 上衣,                 --max(salesNum) 此处必须为聚合函数，
        '裤子' as 裤子,                 --in () 对要转成列的每一个值指定一个列名
        '袜子' as 袜子,
        '帽子' as 帽子
    )
  )
 where 1 = 1;                          --这里可以写查询条件，没有可以直接不要where
```

```sql
with hsb_stat as (select count(1) as num,'已完成重大污染物识别与评价项目' as item from SU_CHECK_ENVWATER_IMPL where STAT_ITEM_ID=110 and FINISH_STATUS=1 and PROJECT_ID=#{project_id}
union
select count(1) as num,'已完成环水保检测项目' as item from SU_CHECK_ENVWATER_IMPL where STAT_ITEM_ID=111 and FINISH_STATUS=1 and PROJECT_ID=#{project_id}
union
select count(1) as num,'已完成“三同时”落实情况项目' as item from SU_CHECK_ENVWATER_IMPL where STAT_ITEM_ID=112 and FINISH_STATUS=1 and PROJECT_ID=#{project_id}
union
select count(1) as num,'已完成环水保验收项目' as item from SU_CHECK_ENVWATER_IMPL where STAT_ITEM_ID=113 and FINISH_STATUS=1 and PROJECT_ID=#{project_id}
union
select nvl(sum(CHECK_COUNT),0) as num,'检查次数' as item from SU_CHECK_ENVWATER_IMPL where PROJECT_ID=#{project_id}
union
select nvl(sum(CHECK_ISSUE_COUNT),0) as num,'发现问题数' as item from SU_CHECK_ENVWATER_IMPL where PROJECT_ID=#{project_id}
union
select nvl(sum(RECTIFY_ISSUE_COUNT),0) as num,'整改完成' as item from SU_CHECK_ENVWATER_IMPL where PROJECT_ID=#{project_id})
-- 重点
select * from hsb_stat pivot(max(num) for item in (
	'已完成“三同时”落实情况项目' as santongshi,
	'已完成环水保检测项目' as hsjc，
	'已完成环水保验收项目' as hsys,
	'已完成重大污染物识别与评价项目' as zdwrw,
	'检查次数' as jccs,
	'整改完成' as zgwc,
	'发现问题数' as fxwts
))
```
+ merge into 合并
```sql
MERGE INTO t1
USING (SELECT id,name FROM t2) t2
ON ( t1.id=t2.id)
WHEN MATCHED THEN
UPDATE SET T1.name= t2.name
WHEN NOT MATCHED THEN
INSERT (id,name) VALUES (t2.id,t2.name);


# 结合with
MERGE INTO #TEMP1 A
USING (
WITH SUMORDER AS 
       (SELECT PRODUCTID, SUM(AMOUNT) TOTAL 
        FROM ORDER GROUP BY PRODUCTID)
       SELECT * FROM SUMORDER
) B ON (A.PRODUCTID = B.PRODUCTID)
WHEN MATCHED THEN UPDATE SET A.TOTAL = B.TOTAL;
```

## 2.2 日期时间
+ 数据库最大的年月往前推12个月
```sql
SELECT
	TO_CHAR(
		ADD_MONTHS(
			TO_DATE( to_char( to_date( ( select max(DECLARE_PERIOD_YEAR_MONTH) from CRZ_NMG_WORKER_WAGE_BOND where project_id=600000000000000138 ), 'yyyy-MM' ), 'yyyy-MM' ), 'yyyy-MM' ),
			ROWNUM - 12 
		),
		'yyyy-MM' 
	) AS MONTHLIST 
FROM
	DUAL CONNECT BY ROWNUM <= 12
```

+ 指定月份的前N个月
```sql
-- 获取2020-06的后5个月（2020-11）
SELECT TO_CHAR(ADD_MONTHS(to_date('2020-06','yyyy-MM'),5),'YYYY-MM') FROM dual;
-- 获取2020-06的前3个月（2020-03）
SELECT TO_CHAR(ADD_MONTHS(to_date('2020-06','yyyy-MM'),-3),'YYYY-MM') FROM dual;
```

+ 返回指定日期当月的最后一天
```sql
SELECT SYSDATE,last_day(SYSDATE) FROM dual;
```

## 2.3 窗口函数
+ over()
```
# 累加
sum(COLLECT_BOND_AMOUNT) over ( ORDER BY DECLARE_PERIOD_YEAR_MONTH desc)
# 分组累加
sum( DESIGN_AMOUNT ) over ( partition BY PROJECT_ID order by DESIGN_AMOUNT desc)
# 在按部门划分的基础上，工资从高到低分级，级别RANK从1开始依次递增
RANK() OVER(PARTITION BY E.DEPTNO ORDER BY E.SAL DESC) RANK
# 记录后第N条
LEAD(E.SAL, 1, 0) OVER(PARTITION BY E.DEPTNO ORDER BY E.SAL) LEAD_SAL
# 记录前面第N行记录
LAG(E.SAL, 1, 0) OVER(PARTITION BY E.DEPTNO ORDER BY E.SAL) LAG_SAL
# 取行号
ROW_NUMBER() OVER(PARTITION BY E.DEPTNO ORDER BY E.SAL) ROW_NUM
# 统计某组中的总计值
SUM(E.SAL) OVER(PARTITION BY E.DEPTNO) SUM_SAL
# 统计某组中的平均值
AVG(E.SAL) OVER(PARTITION BY E.DEPTNO) AVG_SAL
# 按某列分组，并统计该组中记录数量
COUNT(E.SAL) OVER(PARTITION BY E.DEPTNO) COUNT_SAL

```