【第四章】1- 列属性 | Column Attributes「插入, 更新和删除数据」 03:26 2- 插入单行 | Inserting a Row 05:47 3- 插入多行 | Inserting Multiple Rows 03:19 4- 插入分层行 | Inserting Hierarchical Rows 05:54 5- 创建表复制 | Creating a Copy of a Table 08:48 6- 更新单行 | Updating a...
from sqlalchemy import create_engineengine = create_engine("postgresql+psycopg2://scott:tiger@localhost/test")connection = engine.connect()trans = connection.begin()connection.execute(text("insert into x (a, b) values (1, 2)"))trans.commit() 该对象提供了rollback()和commit()方法以控制事务边...
It turned out that many entries in the table 1 and table 2 had string_field column with NULL values. I thought that JOIN would keep records with NULL values because NULL is equal to NULL, isn’t it? Then I tried: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECTNULL=NULL It ...
select *from customerswhere address like ‘%Trail%’ oraddress like ‘%avenue%’LIKE 执行优先级在逻辑运算符之后,毕竟 IN BETWEEN LIKE 本质可看作是比较运算符的简化,应该和比较运算同级,数学→比较→逻辑,始终记住这个顺序,上面这个如果用正则表达式会简单得多 where phone like ‘%9’/where phonenot like...
error occurs if you try to add a new row with a key value that matches an existing row. If you specify a prefix value for a column in a UNIQUE index, the column values must be unique within the prefix length. A UNIQUE index permits multiple NULL values for columns that can contain ...
Sorted Strings Table (borrowed from google) is a file of key/value string pairs, sorted by keys. "An SSTable provides a persistent,ordered immutable map from keys to values, where both keys and values are arbitrary byte strings. Operations are provided to look up the value associated with a...
Checking for ranges like this is very common, so in SQL the BETWEEN keyword provides a useful shorthand for filtering values within a specified range. This query is equivalent to the one above: SELECT title FROM films WHERE release_year ...
CODEPAGE is relevant only if the data contains char, varchar, or text columns with character values more than 127 or less than 32. Important CODEPAGE isn't a supported option on Linux. Note We recommend that you specify a collation name for each column in a format file, except when you...
In table-valued user-defined functions, the PRIMARY KEY constraint can be created on only one column per table. PRIMARY KEY can't be specified for CLR table-valued functions. UNIQUE A constraint that provides entity integrity for a specified column or columns through a unique index. A table ...
Instructs the Query Optimizer to use the average selectivity of the predicate across all column values, instead of using the runtime parameter value when the query is compiled and optimized. If you use OPTIMIZE FOR @variable_name = <literal_constant> and OPTIMIZE FOR UNKNOWN in the same query...