Tag：oracle
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Time：2020-11-27
This is written for Oracle and can be used on different computers, because it will automatically read the environment variables of the current computer, so as to obtain the installation path of Oracle. The only deficiency is that an intermediate text file will be generated during the running process of the program, but this does […]
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Time：2020-11-22
The result is oracleoradb10g_ The home1tnsslistener service cannot be started. There may be three situations: One listener.ora Unable to start due to file configuration error 2. The related environment variables are not set properly 3. When deleting the client, the server’s relevant registry information will be deleted by mistake, resulting in the failure to start […]
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Time：2020-11-21
Hierarchical Queries In Oracle database, there is a method to realize cascade query Select * // the field to query From table // table with child pin ID and parent pin ID Start with selfid = ID // give a startid (the field name is the child pin ID, and the start ID number) Connect […]
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Time：2020-11-20
When designing the database table, we found that Oracle does not have the setting of auto increment primary key. Google understands that Oracle itself does not support auto increment primary key, which needs to be implemented through sequence and trigger. Create table student Create Table Student( ID number (12) primary key, — self increment of […]
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Time：2020-11-19
1. EXTRACT（XMLType_instance，Xpath_string） This function is used to return the corresponding content under the XML node path Example: Copy codeThe code is as follows: SELECT extract(value(a),’/root/main’) data FROM xmltable a ; 2. EXTRACTVALUE（XMLType_instance,Xpath_string) This function returns data for a specific XML node path Example: Copy codeThe code is as follows: Select extractvalue (value (a), ‘/ root […]
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Time：2020-11-18
1. ASCII returns the decimal number corresponding to the specified character; SQL> select ascii(‘A’) A,ascii(‘a’) a,ascii(‘0’) zero,ascii(‘ ‘) space from dual; A A ZERO SPACE ——— ——— ——— ——— 65 97 48 32 2. Chr gives an integer and returns the corresponding character; SQL> select chr(54740) zhao,chr(65) chr65 from dual; ZH C — –Zhao a […]
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Time：2020-11-17
In our normal development, we may encounter the problem of judging whether a column is composed of numbers. We all know that Oracle does not provide us with such a ready-made function. According to my experience, I have summed up two effective methods (column name: column, table name: table) Use the translate + 1 Copy […]
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Time：2020-11-16
Rounding (rounding down) Copy codeThe code is as follows: select floor(5.534) from dual; select trunc(5.534) from dual; Both of the above two usages can round down the number 5. 534 and the result is 5 If you want to round up and get a result of 6, you should use ceil Copy codeThe code is […]
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Time：2020-11-15
The select statement in Oracle can use start with… Connect by prior clause to realize recursive query. Connect by is used in structured query, and its basic syntax is as follows: Copy codeThe code is as follows: select * from tablename start with cond1 connect by cond2 where cond3; In short, a tree structure is […]
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Time：2020-11-14
For example, there is a personnel table (Table Name: peosons)If you want to record the name, ID number and address of the three fields exactly the same, Copy codeThe code is as follows: select p1.* from persons p1,persons p2 where p1.id<>p2.id and p1.cardid = p2.cardid and p1.pname = p2.pname and p1.address = p2.address The above […]
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Time：2020-11-13
Initializing related parameters job_ queue_ processes alter system set job_ queue_ Processes = 39 scope = SPFILE; / / the maximum value cannot exceed 1000; job_ queue_ Interval = 10 / / refresh rate of scheduling jobs in seconds job_ queue_ Process indicates the number of concurrent jobs that Oracle can use show parameter job_queue_process; […]
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Time：2020-11-13
Tiktok’s deal is finally settled! Oracle won an agreement to manage tiktok’s cloud business in the US, and US Treasury Secretary Steven mnuchin confirmed the deal, which means tiktok will continue to operate in the United States. However, the deal is not an acquisition, but Oracle has become tiktok’s “trusted technology partner”. The details of […]
