本文共 9021 字,大约阅读时间需要 30 分钟。
sql关键字
SQL keywords are the reserved words for SQL operations. These Keywords are used across SQL version for different functionalities.
SQL关键字是SQL操作的保留字。 这些关键字在SQL版本中用于不同的功能。
ALTER TABLE table_name ADD column datatype;
Output: On execution of this command a column will get added to the table table_name.
ALTER TABLE :ALTER TABLE用于更改表的列。输出 :执行此命令时,将在表table_name中添加一列。
SELECT column_nameFROM table_nameWHERE column1 = value1AND column2 = value2;
Output: On execution of this command, if column1 is equal to value1 and column2 is equal to value2 then only the row will be qualified for result set.
AND :AND是一个 ,用于添加多个条件。 如果条件连续满足。 它将成为结果集的一部分。输出 :执行此命令时,如果column1等于value1且column2等于value2,则仅该行符合条件集。
SELECT column_name AS 'Alias'FROM table_name;
Output: On execution of this command, the result will display column_name as ‘Alias’.
AS :AS用于别名列或表。输出 :执行此命令时,结果将显示column_name为'Alias'。
SELECT AVG(column_name) FROM table_name;
Output: Execution of this command will provide the average of column_name.
AVG :AVG是一个聚合函数,它将提供数字列的平均值。输出 :执行此命令将提供column_name的平均值。
SELECT column_name(s)FROM table_nameWHERE column_name BETWEEN value1 AND value2;
Output: Execution of this command will give a result set bounded by value1 and value2.
BETWEEN :BETWEEN是用于定义集合的运算符。 范围的值可以是数字,文本和日期。输出 :执行此命令将给出一个以value1和value2为边界的结果集。
SELECT COUNT(column_name) FROM table_name;
Output: On execution of this command, the result will contain the count of the rows for column_name.
COUNT :COUNT是一项功能,可为列提供行数。 该列应为非空列。输出 :执行此命令时,结果将包含column_name的行数。
CREATE TABLE table_name (column1 datatype, column2 datatype);
Output: Execution of this command will result in creation of table with name as table_name along with column1 and column2 as the columns of the table.
CREATE TABLE :此命令用于在数据库中创建表。 它允许指定表的名称以及列的数据类型的名称。输出 :执行此命令将创建名称为table_name的表以及列1和列2作为表的列。
DELETE FROM table_name WHERE column_name = value;
Output: On execution of this command the rows that will be selected based on the condition in the WHERE clause will be deleted.
DELETE :DELETE是用于从表中删除行的命令输出 :执行此命令时,将根据WHERE子句中的条件选择的行将被删除。
SELECT COUNT(*)FROM table_nameGROUP BY column_name;
Output: Execution of this order will result in grouping the result set based on the column_name.
GROUP BY :GROUP BY是SQL中的一个子句,仅与聚合函数一起使用。 它与SELECT语句一起使用,将相同的数据分为几组。输出 :执行此命令将导致根据column_name对结果集进行分组。
SELECT column_name FROM table_1INNER JOIN table_2ON table_1.column_name = table_2.column_name;
Output: Above command will result in rows where both tables have matching values for column_name.
INNER JOIN :INNER JOIN将在两个表中选择具有匹配值的记录。输出 :上面的命令将导致其中两个表的column_name值均匹配的行。
INSERT INTO table_name (column1, column2, column3) VALUES (value1, 'value2', value3);
Output: Execution of this command will result in addition of a new row with values corresponding to the columns.
INSERT :INSERT用于在表中添加新行。输出 :执行此命令将导致添加一个新行,并具有与各列相对应的值。
SELECT column_nameFROM table_nameWHERE column_name LIKE pattern;
Output: Output will the rows that will satisfy the like pattern.
LIKE :LIKE是用于指定模式的运算符。 该运算符与WHERE子句一起使用。输出 :将输出将满足类似模式的行。
SELECT column_nameFROM table_nameLIMIT number;
Output: The resultset will be limited by the number that is provided as part of the limit clause.
LIMIT :LIMIT是一个子句,它允许将结果集行限制为limit子句指定的最大数目。输出 :结果集将受到limit子句中提供的数字的限制。
SELECT MAX(column_name)FROM table_name;
Output: The output will the maximum value specified in the column column_name.
MAX :MAX是一个函数,将从指定的列中返回最大值。输出 :输出将为column_name列中指定的最大值。
SELECT MIN(column_name)FROM table_name;
Output: The output will the minimum value specified in the column column_name.
MIN :MIN是一个函数,将从指定的列中返回最小值。输出 :输出将为列column_name中指定的最小值。
SELECT column_nameFROM table_nameWHERE column_name = value1OR column_name = value2;
Output: Result set will contain rows where column_name value will be either value1 or value2.
OR :OR是用于根据WHERE子句中任一条件的满足选择行的运算符。输出 :结果集将包含column_name值为value1或value2的行。
SELECT column_nameFROM table_nameORDER BY column_name ASC;
Output: On execution of the command above we will get the result set in ascending order.
ORDER BY :ORDER BY用于按数字或字母顺序以升序或降序对列进行排序。输出 :执行上述命令后,我们将获得升序排列的结果集。
SELECT column_name(s) FROM table_1LEFT JOIN table_2ON table_1.column_name = table_2.column_name;
Output: Execution of the command above will result in rows from the table_1 along with rows which satisfies the condition from table_2
Output: Execution of the command above will result in rows from the table_2 along with rows which satisfies the condition from table_1.
LEFT JOIN,RIGHT JOIN :即使不满足联接条件,它们也会合并来自不同表的行。 左/右表中的每一行都返回到结果集中,如果不满足连接条件,则在左/右表的列中填充NULL值。SELECT column_name(s) FROM table_1LEFT JOIN table_2ON table_1.column_name = table_2.column_name;
输出:执行上面的命令将导致table_1中的行以及满足table_2中条件的行
输出:上面命令的执行将导致table_2中的行以及满足table_1中条件的行。
SELECT ROUND(column_name, integer)FROM table_name;
Output: The output of the command will result in rounding up the number based on the integer that is provided as part of the function.
ROUND :ROUND是一个函数,它根据作为函数一部分指定的整数舍入列中指定的数字。输出 :命令的输出将导致根据函数的一部分提供的整数舍入数字。
SELECT column_name FROM table_name
Output: On execution of this command the result set will contain rows for column column_name.
SELECT :SELECT用于从数据库中获取数据。输出 :执行此命令时,结果集将包含column_name列的行。
SELECT DISTINCT column_name FROM table_name;
Output: On execution of the command above the result set will only contain the unique values from the column column_name.
SELECT DISTINCT :SELECT DISTINCT用于从指定的列中检索不同的值。输出 :执行以上命令时,结果集将仅包含column_name列中的唯一值。
SELECT SUM(column_name)FROM table_name;
Output: Execution of this command will result in the total of all the row that are part of the column column_name.
SUM :SUM是一个函数,它将提供数字列的总值。输出 :执行此命令将导致属于列column_name的所有行的总数。
UPDATE table_nameSET some_column = some_valueWHERE some_column = some_value;
Output: Execution of this command will result in updating the row that will satisfy the condition in the where clause.
UPDATE :UPDATE用于更新表的一行的值。输出 :执行此命令将导致更新满足where子句中条件的行。
SELECT column_nameFROM table_nameWHERE column_name operator value;
Output: The output of this command will result in the rows that are satisfying the where clause.
WHERE :WHERE用于指定选择行作为结果集的一部分应满足的条件。输出 :此命令的输出将导致满足where子句的行。
That’s all for a quick roundup on mostly used SQL keywords.
这样就可以快速汇总最常用SQL关键字。
Reference:
参考:
翻译自:
sql关键字
转载地址:http://tymzd.baihongyu.com/