SQL SELECT Database - Learn how to use the SQL SELECT statement to retrieve data from a database effectively. Explore examples and best practices.
SHOW DATABASES; Similarly inSQL Server, the following statement can be used to see the list of available databases. SELECT name FROM sys.databases; Example: Select a database To select a database with nametestDB, the following statement can be used: USE testDB; TheSHOW DATABASES;command can...
[sql1]UNION[ALL|DISTINCT][sql2]UNION[ALL|DISTINCT][sql3]
CREATE DATABASE 语句 CREATE DATABASE 用于创建数据库。 SQL CREATE DATABASE 语法 CREATE DATABASE database_name CREATE TABLE 语句 CREATE TABLE 语句用于创建数据库中的表。 SQL CREATE TABLE 语法 CREATE TABLE 表名称 ( 列名称1 数据类型, 列名称2 数据类型, 列名称3 数据类型, ... ) CREATE TABLE Per...
SELECT [ALL | DISTINCT] [Alias.] Select_Item [AS Column_Name] [, [Alias.] Select_Item [AS Column_Name] ...] FROM [DatabaseName!]Table [Local_Alias] [, [DatabaseName!]Table [Local_Alias] ...] [WHERE JoinCondition [AND JoinCondition ...] [AND | OR FilterCondition [AND | OR...
1 2 3-- select all referencable columns from a table, except a nested field.>SELECT*EXCEPT(c2.b)FROMVALUES(1, named_struct(,,,3))ASt(c1, c2); 1 { "a" : 2 }>*(c2.b, c2.a),,))t(c1, c2); Error: EXCEPT_OVERLAPPING_COLUMNS...
一、基本句式 1. 选取特定的字段作为输出对象 SELECT attr1, attr2, attr3,... FROM tableName; 该语句会按照指令中字段的顺序依次输出对应的数据,另外地,SELECT不会按照特定顺序来检索行。 SELECT installSize, version, ga
CREATE TABLE default.t1 ( `a` Int32, `b` Int32, `c` String, `d` Date ) ENGINE = MergeTree PARTITION BY toYYYYMM(d) ORDER BY (a, b) SETTINGS index_granularity = 8192; 插入测试数据。 INSERT INTO t3(a, b, c, d) INSERT INTO t1(a, b, c, d) VALUES (3,4,'a','2022-09...
CREATE TABLE default.t1 ( `a` Int32, `b` Int32, `c` String, `d` Date ) ENGINE = MergeTree PARTITION BY toYYYYMM(d) ORDER BY (a, b) SETTINGS index_granularity = 8192; 插入测试数据。 INSERT INTO t3(a, b, c, d) INSERT INTO t1(a, b, c, d) VALUES (3,4,'a','2022-09...
Home » SQL Tutorial » SQL SELECT SQL SELECT Summary: in this tutorial, you will learn how to use the basic SQL SELECT statement to query data from a table. When working with a database, querying data from a table is one of the most common tasks that you have to deal with ...