How to use OR condition? Summarize the usage of OR condition examples

I have suffered this loss many times. In the sql code before development, many queries with or as the where condition were even updated. Here are examples to illustrate the disadvantages of using or and how to improve it. select f_crm_id from d_dbname1.t_tbname1 where f_xxx_id = 926067 and (f_mobile ='1234567891' or f_phone ='1234567891' ) limit 1 It is easy to see from the query statement that both fields f_mobile and f_phone may store phone numbers. The general idea is The solution is to use OR to create a sql, but a large amount of table data is simply a disaster: t_tbanme1 has an index idx_id_mobile(

1. MySQL avoids using OR conditions for index columns

Introduction: I have suffered this loss many times. In the sql code before development, many used or as the where condition Query, or even update. Here are examples to illustrate the disadvantages of using or, and how to improve selectf_crm_idfromd_db...

##2. MYSQL AND OR condition problem

Introduction: MYSQL AND OR conditional issues

3. MYSQL AND OR conditional issues

Introduction: MYSQL AND OR condition problem SELECT id,name FROM test WHERE type_1 = 1 OR type_2 = 1 AND id = 1 This will print out all, ignoring the condition id=1, How to change it

4. MySQL or condition can use index to avoid full tableIntroduction: In some cases, or condition can avoid full table Scanned. 1. If there is an or condition in the where statement, the myisam table can use the index, but innodb cannot. 1) Myisam table:

##5.

bitmap index problem in Oracle

Introduction: Bitmap index problem in Oracle, the and and or conditions in the where clause of the query directly correspond to the bitmap (bitmap ) perform Boolean operations to obtain a bitmap result set without the need to convert the bitmap

6.

Analysis of five situations of mysql index failure

Introduction: The index does not take effect all the time. For example, the following situations will cause the index to fail: If there is or in the condition, even if there is a condition with an index, it will not be used. (This is why you should use or as little as possible) Note: If you want to use or and want the index to take effect, you can only add index 2 to each column in the or condition. For multi-column indexes, it is not the first part used

7.

mysql or conditions can use directories to avoid the full table

Introduction: mysql or conditions can use indexes In some cases, the OR condition can avoid a full table scan. ? 1. If there is an or condition in the where statement, the myisam table can use the index, but innodb cannot. 1) myisam table: ?CREATE TABLE IF NOT EXISTS `a` ( ? `id` int(1) NOT NULL AUTO_INCREMENT, ? `uid` i

8.

mysql or conditions can use indexes to avoid full table scans_MySQL

Introduction: mysql or conditions can use indexes to avoid full table scans

9.

About OR conditions and indexes in mysql

Introduction: About OR conditions and indexes in mysql

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