Example 3: Using CASE WHEN in an UPDATE Statement Code: -- Update employee bonuses based on their performance UPDATE employees SET bonus = CASE WHEN performance_rating = 'Excellent' THEN 1000 WHEN performance_rating = 'Good' THEN 500 ELSE 100 END; Explanation: Updates the bonus field based o...
Example 1: How Does the Searched CASE Statement Work in Postgres? In this example, we will apply the CASE statement on the “author_info” table, whose data is shown in the following snippet: SELECT * FROM author_info ORDER BY author_id ASC; In the following statement, we will use the...
Simple CASE Example Suppose you have a table students with a column grades. If you want to classify students based on their grades, a Simple CASE can be handy. Query Demonstration SELECT name, grade, CASE grade WHEN 'A' THEN 'Excellent' WHEN 'B' THEN 'Good' WHEN 'C' THEN 'Average' ...
SELECTCASEatttypidWHEN21/*int2*/THEN16WHEN23/*int4*/THEN32WHEN20/*int8*/THEN64WHEN1700/*numeric*/THENCASEWHENatttypmod=-1THENnullELSE((atttypmod-4)>>16)&65535--calculate the precisionENDWHEN700/*float4*/THEN24/*FLT_MANT_DIG*/WHEN701/*float8*/THEN53/*DBL_MANT_DIG*/ELSEnullENDA...
我们只需要从第一个正斜杠之后开始搜索即可。因此，我们将把第一个正斜杠位置作为起始位置传递给 POSITION 函数。同样，我们将获取文件名和文件扩展名，它们之间的子字符串将包含第二个正斜杠。sql SELECT position('/' in 'http://www.example.com/filename.txt' starting from position('/' in...
An example: GET DIAGNOSTICS integer_var = ROW_COUNT; The second method to determine the effects of a command is to check the special variable named FOUND, which is of type boolean. FOUND starts out false within each PL/pgSQLfunction call. It is set by each of the following types of sta...
一:理论 oracle 截取字符(substr),检索字符位置(instr) case when then else end语句使用 收藏 常用函数:substr和instr 1.SUBSTR(string,start_position,[length]) 求子字符串,返回字符串 解释:string 元字符串 start_position 开始位置(从0开始) length 可选项,子字符串的个数 For example: substr("ABCDEFG",...
For example, if you choose to have one partition per customer and you currently have a small number of large customers, consider the implications if in several years you instead find yourself with a large number of small customers. In this case, it may be better to choose to partition by ...
CREATE INDEX c_idx2 ON locktest(c);ALTER TABLE locktest ADD COLUMN c2 INT;CREATE INDEX c2_idx ON locktest(c2);-- unfinished example transaction BEGIN;UPDATE locktest SETc=3WHEREc=1;-- second connectionpostgres=# SELECT * FROM lockview;pid|vxid|lock_type|lock_mode|granted|xid_lock|rel...
* for example. * 5. Now we have a minimally valid node that can behave correctly * when told to reset or delete itself. We link the node to its * parent (if any), making the node part of the context tree. * 6. We return to the context-type-specific routine, which finishes ...