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Editor to share with you how to use Mysql database condition query statements. I hope you will gain a lot after reading this article. Let's discuss it together.

For analysts, the most common application of Mysql database is the select query statement. This article mainly introduces the query statement of Mysql database.

1. Single table query

1. Conditional query

Basic syntax: select * from + table name + where condition

1) scope query:

Eg:where field between 10 and 100

2) Fuzzy query

Eg:where field like'% is not sure'

Note:% represents multiple characters, _ underscore represents one character, ^ a represents data that begins with a, a $represents data that ends with a, and [abc] matches any character contained. (recommended: MySQL tutorial)

two。 Multi-condition query

Note: when and and or are used at the same time, and takes priority over or. If you want to give priority to the conditions with or, you can use parentheses for some conditions with or.

3. Sort

Basic syntax: order by field.

Remarks: the default is ascending order, ASC ascending order, DESC descending order.

Limit the number of records: limit

4. Aggregate function

Count (): number of statistical records

Avg (): average

Max (): maximum

Min (): minimum

Sum (): summation

5. Grouping

Basic syntax: select field 1, field 2, aggregate function from + table name + group by field 1, field 2

Note: group by and having are used together to filter grouping results.

Second, multi-table association query

1. Internal connection-- > inner join

An inner join is an equivalent connection, which can be omitted as join to obtain the records of the matching relationship between the fields in the two tables.

It can be understood as the "intersection" in the concept of set, and the associated field has records with two tables at the same time.

two。 Left connection-- > left join

Join to the left to get all the records of the main table on the left, even if there is no corresponding data in the right table.

3. Right connection-- > right join

Connect to the right to get all the records of the main table on the right, even if there is no corresponding data in the left table.

4. Connector-- > union

Union is used to concatenate the results of more than two select statements, combine the results into a result set, and delete duplicate data

Basic syntax: select field from Table 1 union [all | distinct] select Field from Table 2

Note: union means that if union distinct; is union all, the result set with duplicate data is returned; when using union, the selected display will be named after the field name of the previous table.

After reading this article, I believe you have a certain understanding of how to use Mysql database condition query statements, want to know more about it, welcome to follow the industry information channel, thank you for your reading!

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