SQL 小技巧

不定時更新，歡迎交流指正

Oracle

1.浮點數轉為字元

trim('.' from to_char(xxx,'fm999990.99'))

2.查詢當前使用者下各表大小

檢視資料庫表空間儲存物件的大小

SELECT *
  FROM (SELECT SEGMENT_NAME,
               T.SEGMENT_TYPE,
               round(SUM(BYTES) / 1024 / 1024/1024
 
,2) SEGMENT_SIZE
          FROM USER_SEGMENTS T
         GROUP BY T.SEGMENT_NAME, T.SEGMENT_TYPE) T
 ORDER BY SEGMENT_SIZE DESC;

實際表佔用空間大小，包括表所屬物件：INDEX、LOBINDEX、LOBSEGMENT

SELECT *
  FROM (SELECT SEGMENT_NAME,
               SEGMENT_TYPE,
               ROUND(SUM(BYTES) / 1024 / 1024 / 1024, 2) SEGMENT_SIZE
          FROM
 
 (SELECT T.TABLESPACE_NAME,
                       T.SEGMENT_NAME,
                       T.SEGMENT_TYPE,
                       T.BYTES
                  FROM USER_SEGMENTS T
                 WHERE T.SEGMENT_TYPE NOT IN
                       ('INDEX', 'LOBINDEX', 'LOBSEGMENT')
                UNION
 
 ALL
                SELECT T.TABLESPACE_NAME,
                       UL.TABLE_NAME AS SEGMENT_NAME,
                       'TABLE' AS SEGMENT_TYPE,
                       T.BYTES
                  FROM USER_SEGMENTS T
                 INNER JOIN USER_LOBS UL
                    ON T.SEGMENT_NAME = UL.SEGMENT_NAME
                 WHERE T.SEGMENT_TYPE = 'LOBSEGMENT'
                UNION ALL
                SELECT T.TABLESPACE_NAME,
                       UI.TABLE_NAME AS SEGMENT_NAME,
                       'TABLE' AS SEGMENT_TYPE,
                       T.BYTES
                  FROM USER_SEGMENTS T
                 INNER JOIN USER_INDEXES UI
                    ON T.SEGMENT_NAME = UI.INDEX_NAME
                 WHERE T.SEGMENT_TYPE IN ('INDEX', 'LOBINDEX')) T
         GROUP BY SEGMENT_NAME, SEGMENT_TYPE) T
 ORDER BY SEGMENT_SIZE DESC;

參考地址

3.PL/SQL 匯入CSV檔案前建議先查一下字元編碼

select userenv(‘language’) from dual;

得到字元編碼後再將csv檔案做對應字元編碼轉換，避免不必要的時間浪費

本文來自部落格園，作者：Splus，轉載請註明原文連結：https://www.cnblogs.com/s-plus/p/15889932.html