Oracle Sql In Clause

We want to do not only write SQL, but also to do a good performance of the SQL, the following for the author to learn, extract, and summarized part of the information to share with you! (1) Select the most efficient table name order (valid only in the Rule-based optimizer): The ORACLE parser processes the table names in the FROM clause in Right-to-left order, and the last table in the FROM clause (the underlying table driving tables) is processed first, In the case where multiple tables are included in the FROM clause, you must select the table with the least number of records as the underlying table. If...

SQL statement for querying and deleting duplicate records (i) For example, there is a field "name" in Table A, and the "name" value may be the same between different records, and now you need to query between the records in the table, the "name" value has duplicates, and select name, Count (*) from-a group by name has count (*) > 1 as ...

Method 1 delete yourtable where [id] not in (select max ([id]) from yourtable group by (name + value) b on a.id = b.id where b.id ...

When companies consider cloud computing services, every good project manager should ask the following questions: "Who is my data in the cloud?" "What happens when I need to migrate this data?" "For private clouds, hardware, software and data are all inside the company, so ownership is clear." However, there are a number of complex issues to consider when migrating data to the outside of a private cloud. The entire industry is focused on cloud security, privacy and dominance. The blurring of data ownership is the root cause of all cloud-related problems. Consider whether the data exists ...

CSDN Web site was exposed more than 6 million users after the leak, 51CTO, CNZZ, enet, U-uu9, yy voice, Lily Nets, happy net (micro-bo), Renren, the United States and space network, precious nets and many other well-known websites have been plunged into the user data leakage. 　　 　　The total number of leaked accounts is estimated to be over 200 million, and may indirectly affect the information security of a total of 500 million accounts because users use the same registration name, mailbox, and password on other sites that are not compromised. As the current Internet applications are used to communicate or publish information, users stored in the operator's private data relative and ...