From b2cca108a349ae4a5fa10eee560734f04a35a56d Mon Sep 17 00:00:00 2001
From: Ganlin Zhao <ganlinzhao@hotmail.com>
Date: Tue, 18 Apr 2023 14:29:04 +0800
Subject: [PATCH] add documentations

---
 docs/en/12-taos-sql/10-function.md | 10 ++++++++--
 docs/zh/12-taos-sql/10-function.md | 10 ++++++++--
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/docs/en/12-taos-sql/10-function.md b/docs/en/12-taos-sql/10-function.md
index 8dfa9c2851..5c1a833e05 100644
--- a/docs/en/12-taos-sql/10-function.md
+++ b/docs/en/12-taos-sql/10-function.md
@@ -459,12 +459,17 @@ TO_JSON(str_literal)
 #### TO_UNIXTIMESTAMP
 
 ```sql
-TO_UNIXTIMESTAMP(expr)
+TO_UNIXTIMESTAMP(expr [, return_timestamp])
+
+return_timestamp: {
+    0
+  | 1
+}
 ```
 
 **Description**: UNIX timestamp converted from a string of date/time format
 
-**Return value type**: BIGINT
+**Return value type**: BIGINT, TIMESTAMP
 
 **Applicable column types**: VARCHAR and NCHAR
 
@@ -476,6 +481,7 @@ TO_UNIXTIMESTAMP(expr)
 
 - The input string must be compatible with ISO8601/RFC3339 standard, NULL will be returned if the string can't be converted
 - The precision of the returned timestamp is same as the precision set for the current data base in use
+- return_timestamp indicates whether the returned value type is TIMESTAMP or not. If this parameter set to 1, function will return TIMESTAMP type. Otherwise function will return BIGINT type. If parameter is omitted, default return value type is BIGINT.
 
 
 ### Time and Date Functions
diff --git a/docs/zh/12-taos-sql/10-function.md b/docs/zh/12-taos-sql/10-function.md
index 94f8052051..50e82e6b90 100644
--- a/docs/zh/12-taos-sql/10-function.md
+++ b/docs/zh/12-taos-sql/10-function.md
@@ -459,12 +459,17 @@ TO_JSON(str_literal)
 #### TO_UNIXTIMESTAMP
 
 ```sql
-TO_UNIXTIMESTAMP(expr)
+TO_UNIXTIMESTAMP(expr [, return_timestamp])
+
+return_timestamp: {
+    0
+  | 1
+}
 ```
 
 **功能说明**：将日期时间格式的字符串转换成为 UNIX 时间戳。
 
-**返回结果数据类型**：BIGINT。
+**返回结果数据类型**：BIGINT, TIMESTAMP。
 
 **应用字段**：VARCHAR, NCHAR。
 
@@ -476,6 +481,7 @@ TO_UNIXTIMESTAMP(expr)
 
 - 输入的日期时间字符串须符合 ISO8601/RFC3339 标准，无法转换的字符串格式将返回 NULL。
 - 返回的时间戳精度与当前 DATABASE 设置的时间精度一致。
+- return_timestamp 指定函数返回值是否为时间戳类型，设置为1时返回 TIMESTAMP 类型，设置为0时返回 BIGINT 类型。如不指定缺省返回 BIGINT 类型。
 
 
 ### 时间和日期函数