1.22. SQLite Limit clause

发布时间 :2024-01-11 23:00:02 UTC      

SQLite’s LIMIT Clause is used to restrict the value of the SELECT The amount of data returned by the statement.

1.22.1. Grammar

With LIMIT Of the clause SELECT The basic syntax of the statement is as follows:

SELECT column1, column2, columnN
FROM table_name
LIMIT [no of rows]

The following is LIMIT Clause vs. OFFSET Syntax when using clauses together:

SELECT column1, column2, columnN
FROM table_name
LIMIT [no of rows] OFFSET [row num]

The SQLite engine will return from the next line until the given OFFSET All lines up to now, as shown in the last example below.

1.22.2. Example

Hypothetical COMPANY The table has the following records:

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0
7           James       24          Houston     10000.0

Here is an example that limits the number of rows you want to extract from the table:

sqlite> SELECT * FROM COMPANY LIMIT 6;

This will produce the following results:

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall  45000.0

However, in some cases, you may need to extract the record from a specific offset. The following is an example of extracting three records from the third bit:

sqlite> SELECT * FROM COMPANY LIMIT 3 OFFSET 2;

This will produce the following results:

ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0

Principles, Technologies, and Methods of Geographic Information Systems  102

In recent years, Geographic Information Systems (GIS) have undergone rapid development in both theoretical and practical dimensions. GIS has been widely applied for modeling and decision-making support across various fields such as urban management, regional planning, and environmental remediation, establishing geographic information as a vital component of the information era. The introduction of the “Digital Earth” concept has further accelerated the advancement of GIS, which serves as its technical foundation. Concurrently, scholars have been dedicated to theoretical research in areas like spatial cognition, spatial data uncertainty, and the formalization of spatial relationships. This reflects the dual nature of GIS as both an applied technology and an academic discipline, with the two aspects forming a mutually reinforcing cycle of progress.