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See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at',source:"@site/versioned_docs/version-2.1/sql-manual/sql-functions/window-functions/window-function-first-value.md",sourceDirName:"sql-manual/sql-functions/window-functions",slug:"/sql-manual/sql-functions/window-functions/window-function-first-value",permalink:"/docs/sql-manual/sql-functions/window-functions/window-function-first-value",draft:!1,tags:[],version:"2.1",frontMatter:{title:"WINDOW_FUNCTION_FIRST_VALUE",language:"en"},sidebar:"docs",previous:{title:"WINDOW_FUNCTION_CUME_DIST",permalink:"/docs/sql-manual/sql-functions/window-functions/window-function-cume-dist"},next:{title:"WINDOW_FUNCTION_LAST_VALUE",permalink:"/docs/sql-manual/sql-functions/window-functions/window-function-last-value"}},s={},u=[{value:"WINDOW FUNCTION FIRST_VALUE",id:"window-function-first_value",level:2},{value:"description",id:"description",level:3},{value:"example",id:"example",level:3},{value:"keywords",id:"keywords",level:3}],c={toc:u},d="wrapper";function f(e){let{components:n,...t}=e;return(0,o.yg)(d,(0,r.A)({},c,t,{components:n,mdxType:"MDXLayout"}),(0,o.yg)("h2",{id:"window-function-first_value"},"WINDOW FUNCTION FIRST_VALUE"),(0,o.yg)("h3",{id:"description"},"description"),(0,o.yg)("p",null,"FIRST_VALUE() returns the first value in the window's range , ignore_null determines whether to ignore null values , the ignore_null of default value is false ."),(0,o.yg)("pre",null,(0,o.yg)("code",{parentName:"pre",className:"language-sql"},"FIRST_VALUE(expr[, ignore_null]) OVER(partition_by_clause order_by_clause [window_clause])\n")),(0,o.yg)("h3",{id:"example"},"example"),(0,o.yg)("p",null,"We have the following data"),(0,o.yg)("pre",null,(0,o.yg)("code",{parentName:"pre",className:"language-sql"}," select id, myday, time_col, state from t;\n \n | id | myday | time_col | state |\n |------|-------|-------------|-------|\n | 3 | 21 | 04-21-13 | 3 |\n | 7 | 22 | 04-22-10-24 | NULL |\n | 8 | 22 | 04-22-10-25 | 9 |\n | 10 | 23 | 04-23-12 | 10 |\n | 4 | 22 | 04-22-10-21 | NULL |\n | 9 | 23 | 04-23-11 | NULL |\n | 1 | 21 | 04-21-11 | NULL |\n | 5 | 22 | 04-22-10-22 | NULL |\n | 12 | 24 | 02-24-10-21 | NULL |\n | 2 | 21 | 04-21-12 | 2 |\n | 6 | 22 | 04-22-10-23 | 5 |\n | 11 | 23 | 04-23-13 | NULL |\n")),(0,o.yg)("p",null,"Use FIRST_VALUE() to group by myday and return the value of the first state in each group:"),(0,o.yg)("pre",null,(0,o.yg)("code",{parentName:"pre",className:"language-sql"},"select * , \nfirst_value(`state`, 1) over(partition by `myday` order by `time_col` rows between 1 preceding and 1 following) as ignore_null,\nfirst_value(`state`, 0) over(partition by `myday` order by `time_col` rows between 1 preceding and 1 following) as not_ignore_null,\nfirst_value(`state`) over(partition by `myday` order by `time_col` rows between 1 preceding and 1 following) as ignore_null_default\nfrom t order by `id`, `myday`, `time_col`;\n\n| id | myday | time_col | state | ignore_null | not_ignore_null | ignore_null_default |\n|------|-------|-------------|-------|-------------|-----------------|---------------------|\n| 1 | 21 | 04-21-11 | NULL | 2 | NULL | NULL |\n| 2 | 21 | 04-21-12 | 2 | 2 | NULL | NULL |\n| 3 | 21 | 04-21-13 | 3 | 2 | 2 | 2 |\n| 4 | 22 | 04-22-10-21 | NULL | NULL | NULL | NULL |\n| 5 | 22 | 04-22-10-22 | NULL | 5 | NULL | NULL |\n| 6 | 22 | 04-22-10-23 | 5 | 5 | NULL | NULL |\n| 7 | 22 | 04-22-10-24 | NULL | 5 | 5 | 5 |\n| 8 | 22 | 04-22-10-25 | 9 | 9 | NULL | NULL |\n| 9 | 23 | 04-23-11 | NULL | 10 | NULL | NULL |\n| 10 | 23 | 04-23-12 | 10 | 10 | NULL | NULL |\n| 11 | 23 | 04-23-13 | NULL | 10 | 10 | 10 |\n| 12 | 24 | 02-24-10-21 | NULL | NULL | NULL | NULL |\n")),(0,o.yg)("h3",{id:"keywords"},"keywords"),(0,o.yg)("pre",null,(0,o.yg)("code",{parentName:"pre"},"WINDOW,FUNCTION,FIRST_VALUE\n")))}f.isMDXComponent=!0}}]); |