Does SQL have a notation?

SQL has the "% symbol" in it.

In SQL SQL, "%" indicates a wildcard character.

For example: like'db\%i'escape'\'The meaning of this sentence is:

Look for something like db%i, where is a swap character, so % is escaped to a normal % character, and this method works well with the wildcard character '-'

For example, select * from student table where name like'%[%'

There are the following results:

2009121001 Jia %tao, male, 1992-11-02, Zhengzhou, Henan 005, 2003

2009121002 Li Ming% Female 1989-06-03 Jiaozuo, Henan 001 2001

Wildcard Details:].

Use wildcards as text.

You can use a wildcard pattern matching string as a literal string by placing the wildcard in parentheses. The following table shows an example of using the like keyword and the [ wildcard.

Symbol meaning.

like '5[%]' 5%

like '[_]n' _n

like '[a-cdf]'A, B, C, D, or F

like '[-acdf]'-, a, c, d, or f

like '[ [' [

like ']' ]

like 'abc[_]d%'ABC D and ABC DE

like 'abc[def]'ABCD, ABCE, and ABCF

In the select statement, (+) refers to an outer join, which is a method of joining a query.

Example: select t1*,t2.* from dept t1,emp t2 where

Where: means that even if there is no matching record in T2 (EMP table), it is queried in T1 (DIPT table).

The SQL language is a structured query language.

Structured Query Language).

The SQL language is a database query and programming language.

for accessing data and querying, updating, and managing relational database systems; It is also an extension for database script files.

SQL statements used in Oracle databases can be added after the table (+) to implement an outer join.

The query result is based on the primary table, that is, if there are no records in the slave table that meet the conditions of the primary table, blank rows are displayed to join the primary table.

For example, Tablea A, Tableb B

The result of the query is:

SQL statementA symbol means a connection, which is equivalent to a connector in a string.

Common symbols in SQL:

1, = means equal.

2. <> means that it is not equal to.

3. > means greater than.

4. < means less than.

5. >= indicates greater than or equal to.

6. <= means less than or equal to.

7. between means within a certain range.

SQL statementA symbol means a connection, which is equivalent to a connector in a string.

Common symbols in SQL:

1, = means equal.

2. <> means that it is not equal to.

3. > means greater than.

4. < means less than.

5. >= indicates greater than or equal to.

6. <= means less than or equal to.

7. between means within a certain range.

SQL statementA symbol means a connection, which is equivalent to a connector in a string.

Common symbols in SQL:

1, = means equal.

2. <> means that it is not equal to.

3. > means greater than.

4. < means less than.

5. >= indicates greater than or equal to.

6. <= means less than or equal to.

7. between means within a certain range.

1. There are two ways to express non-equals in SQL, and one is"<>without quotation marks), the other is"!= without quotation marks), the usage is the same.

2. That is, where a <>100; Or where a !=100;

Structured Query Language (SQL) is abbreviated as SQL (pronounced: es kju el"s-q-l"), a special-purpose programming language, is a database query and programming language for accessing data and querying, updating, and managing relational database systems; It is also an extension for database script files.

Structured Query Language is a high-level, non-procedural programming language that allows users to work on high-level data structures. It does not require the user to specify the storage method of the data, nor does it require the user to understand the specific data storage method, so different database systems with completely different underlying structures can use the same structured query language Yanzhi preface as the interface for data input and management. Structured Query Language statements can be nested, which makes it extremely flexible and powerful.