Mining pit record of modified field information in Dameng database

1. summary

• Purpose ： Modify all tables in the tablespace xxx Length of field .
• Realization ： adopt SQL Make changes .
• problem ： The navigation bar — Pattern — Table space — surface — Right click to view the table information , The field length has not been modified to .
• Tools ：DM Management tools （ Dameng's own database management tool ）.

2. The process

2.1 Problems arise

--  adopt SQL Find out xx A table whose field length meets the requirements , Concatenate the modified field length SQL
SELECT 'ALTER TABLE ' || t.table_name || ' MODIFY xxx VARCHAR(1);'  AS str
  FROM user_tab_columns t 
  WHERE t.column_name='xxx' AND t.data_length > 1;
 --  Perform the spliced SQL, View table properties , The field length has not changed .

2.2 Refresh 、 Transaction commit attempt

Refresh table 、 Table space 、 Pattern 、 The connection has no effect . Looks like a big move , Restart the tool ; Close tooltip transaction not committed , That's the reason . perform COMMIT, Not yet. （ Later, we found that this transaction is a query statement (╯︵╰)）.

2.3 Check SQL

SQL I didn't write it right , Fall into self doubt （ I'm using Oracle Of SQL sentence ）. We can only see what the official documents of Damon say .

--  In document SQL  Example ：
ALTER TABLE PRODUCTION.PRODUCT_REVIEW MODIFY NAME VARCHAR(8) ;

sql No problem .

2.4 Verify that the table information of the navigation bar is not updated

• Through the initial query SQL, It is found that there is no data whose field length does not meet the requirements .
• adopt idea Of database Connect to database , It is found that the field length has been modified to .

3. summary

Daydream “DM Management tools ” A pit .
Directly modify the field length in the table attribute to ; use SQL modify , The navigation bar cannot be modified , But in fact, the modification was successful .
SQL How to update after modification , There is no way to refresh .

4. Problem solving

SQL There is no schema to get the table name in （ Schema name .table_name） Why , Only when the schema name is written will the field information in the navigation bar table attribute be updated （ Although the schema name in the document is optional , It's ok if you don't write ）.