SQL---CASE WHEN条件表达式(conditional statement) CASE表达式是用来判断条件的,条件成立时返回某个值,条件不成立时返回另一个值。 语法: CASEWHENComparsionConditionTHENresultWHENComparsionConditionTHENresultELSEotherEND (注:各分支返回的数据类型需一致。) (注:when子句一定要有排他性,因为当when子句为真时,剩余...
WHERE IN Flexibility It allows us to set different values in a single query It allows us to update a single value to match the records Performance Due to the conditional checks, it is slower Since the same value is assigned to every row, it is faster Method 3: Updating Multiple Columns ...
perform a conditional update or insert operation (MERGE), see an execution plan of SQL (EXPLAIN PLAN), and lock a table to restrict access (LOCK TABLE). --DDL--Data Definition Language--数据定义语言 create, modify,drop, or rename objects (CREATE,ALTER,DROP,RENAME), remove all rows from ...
Conditional WHERE clauses using “OR ... IS NULL” cause SQL performance problems. Don’t try to outsmart the database.
CASE WHEN condition1 THEN statement1, WHEN condition2 THEN statement2, WHEN condition THEN statementN ELSE result END; Where, condition1, condition2, etc. Are the conditional statements and statement1, statement2, etc.. are the actions to be taken when the condition is true....
The following is example using the IF-THEN-ELSE statement in an Oracle function: CREATE OR REPLACE Function IncomeLevel ( name_in IN varchar2 ) RETURN varchar2 IS monthly_value number(6); ILevel varchar2(20); cursor c1 is SELECT monthly_income FROM employees WHERE name = name_in; BEGIN...
SQL_TIMESTAMP、SQL_TINYINT、 SQL_TSI_DAY、SQL_TSI_FRAC_SECOND、SQL_TSI_HOUR、SQL_TSI_MICROSECOND、SQL_TSI_MINUTE、SQL_TSI_MONTH、 SQL_TSI_QUARTER、 SQL_TSI_SECOND、SQL_TSI_WEEK、SQL_TSI_YEAR、SQL_VARBINARY、SQL_VARCHAR、STATE、STATEMENT、STRING_AGG、STRUCTURE、STYLE、SUBCLASS_ORIGIN、...
Both the DECODE statement and the CASE expression perform conditional tests. When the value in test_value matches any following expression, the related value is returned. If no match is found, the default_value is returned. If no default_value is specified, both DECODE and CASE return NULL if...
SQL Where Clauses Look at this SQL programming example. The Where clause is optional and specifies which data values or rows will be returned or displayed, based on the criteria described after the keyword Where. Where Conditional Selections Conditional selections used in the Where clause are: ...
问如何使用条件语句在Hive/SQL中执行(或绕过)代码块？EN客户需求是咨询如何用SQL结合decode函数实现条件...